From cb7bcfad4ab0041aaf3fde3185e27ee46bb37788 Mon Sep 17 00:00:00 2001 From: JSDurand Date: Tue, 15 Nov 2022 12:01:28 +0800 Subject: Initial commit Basic GNU standard files are added, and we now stop worrying about monadic anamorphisms. The current focus is on testing the correctness of the algorithm, so I need convenient support for manipulating, interpreting, examining, and per chance animating nondeterministic automata. --- AUTHORS | 1 + COPYING | 674 +++++++++++++++++++++++++++++++++++++++++++++++ Cargo.toml | 36 +++ ChangeLog | 21 ++ DESIGN.org | 114 ++++++++ INSTALL | 368 ++++++++++++++++++++++++++ Makefile.am | 1 + NEWS | 1 + README | 3 + THANKS | 0 benches/bench_receme.rs | 293 ++++++++++++++++++++ configure.ac | 28 ++ find-version.sh | 20 ++ graph/Cargo.toml | 12 + graph/Makefile.am | 12 + graph/src/adlist.rs | 181 +++++++++++++ graph/src/adset.rs | 229 ++++++++++++++++ graph/src/error.rs | 26 ++ graph/src/labelled.rs | 426 ++++++++++++++++++++++++++++++ graph/src/lib.rs | 203 ++++++++++++++ nfa/Cargo.toml | 13 + nfa/src/default/mod.rs | 123 +++++++++ nfa/src/error.rs | 30 +++ nfa/src/lib.rs | 94 +++++++ receme/Cargo.toml | 9 + receme/src/algebra.rs | 14 + receme/src/catana.rs | 27 ++ receme/src/coalgebra.rs | 14 + receme/src/coralgebra.rs | 28 ++ receme/src/functor.rs | 64 +++++ receme/src/hylo.rs | 41 +++ receme/src/lib.rs | 227 ++++++++++++++++ receme/src/parapo.rs | 44 ++++ receme/src/ralgebra.rs | 25 ++ receme/src/tree.rs | 368 ++++++++++++++++++++++++++ repcore/Cargo.toml | 8 + repcore/src/lib.rs | 14 + src/lib.rs | 14 + 38 files changed, 3806 insertions(+) create mode 100644 AUTHORS create mode 100644 COPYING create mode 100644 Cargo.toml create mode 100644 ChangeLog create mode 100644 DESIGN.org create mode 100644 INSTALL create mode 100644 Makefile.am create mode 100644 NEWS create mode 100644 README create mode 100644 THANKS create mode 100644 benches/bench_receme.rs create mode 100644 configure.ac create mode 100755 find-version.sh create mode 100644 graph/Cargo.toml create mode 100644 graph/Makefile.am create mode 100644 graph/src/adlist.rs create mode 100644 graph/src/adset.rs create mode 100644 graph/src/error.rs create mode 100644 graph/src/labelled.rs create mode 100644 graph/src/lib.rs create mode 100644 nfa/Cargo.toml create mode 100644 nfa/src/default/mod.rs create mode 100644 nfa/src/error.rs create mode 100644 nfa/src/lib.rs create mode 100644 receme/Cargo.toml create mode 100644 receme/src/algebra.rs create mode 100644 receme/src/catana.rs create mode 100644 receme/src/coalgebra.rs create mode 100644 receme/src/coralgebra.rs create mode 100644 receme/src/functor.rs create mode 100644 receme/src/hylo.rs create mode 100644 receme/src/lib.rs create mode 100644 receme/src/parapo.rs create mode 100644 receme/src/ralgebra.rs create mode 100644 receme/src/tree.rs create mode 100644 repcore/Cargo.toml create mode 100644 repcore/src/lib.rs create mode 100644 src/lib.rs diff --git a/AUTHORS b/AUTHORS new file mode 100644 index 0000000..9ce63ba --- /dev/null +++ b/AUTHORS @@ -0,0 +1 @@ +Jean Sévère Durand \ No newline at end of file diff --git a/COPYING b/COPYING new file mode 100644 index 0000000..e72bfdd --- /dev/null +++ b/COPYING @@ -0,0 +1,674 @@ + GNU GENERAL PUBLIC LICENSE + Version 3, 29 June 2007 + + Copyright (C) 2007 Free Software Foundation, Inc. + Everyone is permitted to copy and distribute verbatim copies + of this license document, but changing it is not allowed. + + Preamble + + The GNU General Public License is a free, copyleft license for +software and other kinds of works. + + The licenses for most software and other practical works are designed +to take away your freedom to share and change the works. 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It is safest +to attach them to the start of each source file to most effectively +state the exclusion of warranty; and each file should have at least +the "copyright" line and a pointer to where the full notice is found. + + + Copyright (C) + + This program is free software: you can redistribute it and/or modify + it under the terms of the GNU General Public License as published by + the Free Software Foundation, either version 3 of the License, or + (at your option) any later version. + + This program is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + GNU General Public License for more details. + + You should have received a copy of the GNU General Public License + along with this program. If not, see . + +Also add information on how to contact you by electronic and paper mail. + + If the program does terminal interaction, make it output a short +notice like this when it starts in an interactive mode: + + Copyright (C) + This program comes with ABSOLUTELY NO WARRANTY; for details type `show w'. + This is free software, and you are welcome to redistribute it + under certain conditions; type `show c' for details. + +The hypothetical commands `show w' and `show c' should show the appropriate +parts of the General Public License. Of course, your program's commands +might be different; for a GUI interface, you would use an "about box". + + You should also get your employer (if you work as a programmer) or school, +if any, to sign a "copyright disclaimer" for the program, if necessary. +For more information on this, and how to apply and follow the GNU GPL, see +. + + The GNU General Public License does not permit incorporating your program +into proprietary programs. If your program is a subroutine library, you +may consider it more useful to permit linking proprietary applications with +the library. If this is what you want to do, use the GNU Lesser General +Public License instead of this License. But first, please read +. \ No newline at end of file diff --git a/Cargo.toml b/Cargo.toml new file mode 100644 index 0000000..e672e74 --- /dev/null +++ b/Cargo.toml @@ -0,0 +1,36 @@ +[package] +name = "rep" +version = "0.1.0" +edition = "2021" +authors = ["JSDurand "] +description = "Rust, Emacs, and Parsers" +license = "GPL-3.0-or-later" +keywords = ["emacs", "parser"] +# We require a minimal Rust version of 1.65 as we need the feature of +# generic associated types, which are not stablized until version +# 1.65. +rust-version = "1.65" +# testing the new resolver, even though this has no dependencies ;p + +[workspace] +members = ["graph", "receme", "nfa", "repcore"] +resolver = "2" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] +receme = { path = "receme" } + +[dev-dependencies] +criterion = "0.4" + +[features] +default = [] +tokenizer = [] + +[profile.bench] +debug = true + +[[bench]] +name = "bench_receme" +harness = false diff --git a/ChangeLog b/ChangeLog new file mode 100644 index 0000000..a064c8c --- /dev/null +++ b/ChangeLog @@ -0,0 +1,21 @@ +2022-11-15 Jean Sévère Durand + + * nfa: Stop worrying about monadic anamorphisms. + + I was trying to design a way to use monadic anamorphisms to build + and parse regular expressions. But, after some more thoughts, I + can only think about implementations that affect the performance + and are quite specifically tailored to my use-cases. This means + the design is neither efficient nor generic. So what is the use + of it anyways? + + In the end, I decided to mildly generalize my usual pattern of + recursive descent parsing. After all, my current focus is to + implement a version of NFA that can show me derivatives of the + atomic languages in a human-friendly and easy-to-use way. This + will help me catch errors in my algorithms. + +2022-11-13 Jean Sévère Durand + + * gnu-standards: Add basic files required by the GNU standard. + diff --git a/DESIGN.org b/DESIGN.org new file mode 100644 index 0000000..18834cb --- /dev/null +++ b/DESIGN.org @@ -0,0 +1,114 @@ +#+AUTHOR: Durand +#+EMAIL: durand@jsdurand.xyz +#+DATE: <2022-09-30 Ven 14:45> +#+STARTUP: fold + +This document records an attempt to design a parser generator library. + +* Goals + +- Modular + + The library should be modular enough that the following components + of the parser generator can be easily substituted by either external + crates or even external foreign functions. + + + Regular expression matchers + + This project is to have a parser generator. A regular expression + matcher is not the core goal of the project. So I shall write the + library in a way that can use other means to match regular + expressions, should some users wish to do so. + + Since I do not want to use external dependencies by default, I + will also write a small regular expression matcher library to + serve as the default matcher. This will allow me to try different + optimization techniques for regular expression matchers as well. + + + Nondeterministic Fintie Automata + + The project needs to manipulate nondeterministic fintie automata. + As for regular expression matchers, I will write my own library + for dealing with NFA's, and in the mean time preserve the + possibility to "plug in" other external crates for this purpose as + well. + + + Graph data type + + The internal data of the parser generator, as used by the current + algorithm, is a directed graph. While this is easy to represent + using the adjacent list representation, I will not underestimate + the potential optimizations brought by external libraries. + + Moreover, the underlying data structures of regular expressions + and nondeterministic fintie automata are graphs as well. So they + should be able to share the same data structure in the default + implementation, and to plug in external crates, should the need + arise. + +- Abstract + + One of the deficiencies of the current version of this project is + that it does not mirror the abstract ideas of the algorithm closely. + This means that, when the implementation of the algorithm goes + wrong, I cannot precisely pinpoint the cause for the erraneous + behaviour. + + The reason for the departure from the abstract ideas was that I + thought this could lead to some performance gains. Apparently I was + too obsessed with premature optimizations that I ignored the + potential problems caused. + +** Update + +Now I realize that a nondeterministic fintie automaton is equivalent +with a regular expression, so it makes no sense to deal with NFAs +without dealing with regular expressions. Also, dealing with regular +expressions directly makes it easier to extract the "atomic languages" +of grammars and to present them in a readable way. + +But still the current focus is not on matching regular expressions, +but on the structures of regular expressions. + +* Details + +According to the above goals, I have to write three sub-crates, or +workspace members, for regular expression matchers, NFA's, and for +graphs, respectively. + +Each of these three crates is easy to write, in my opinion. I just +have to pack the old codes into separate crates, to separate concerns. +Once this is done, I can easily plug in other crates as well, as one +can just wrap up external crates. + +Moreover, in order to achieve the goal of abstraction, I need modules +for "atoms" and "languages". Atoms represent the regular language of +derivatives of the grammar. This is perhaps the most obscure part, in +my experience. Languages represent the derivative of the grammar with +respect to inputs. From my experience, it is not a good idea to +calculate the semiring values after the derivatives have been +calculated. Instead, we shall calculate the semiring values at the +same time as calculating the derivatives of the grammar, and record +the values in a dedicated recorder. + +* Tokenizers + +In my opinion, tokenization is just a speed-up process. The user +should not worry about the distinction between tokens and +non-terminals. This means I want the parser generator to work at the +character, or byte, level by default. When the user wants to use a +dedicated tokenizer, to have some speed-ups for example, the user can +supply a function that eats a string, or an array of bytes, and +returns an array of tokens. + +This decision means that we don't need regular expressions by default. +We shall add the regular expressions back later, when we want to +decrease the constant factor involved in the algorithmic complexities. +When we do want to do so, then, we need a way to automatically deduce +regular expression terminals. In the current version, a non-terminal +whose rules only involve with terminals will be automatically +converted to a regular expression terminal. I think this mechanism +can be adapted in the future. + +* Grammars + diff --git a/INSTALL b/INSTALL new file mode 100644 index 0000000..8865734 --- /dev/null +++ b/INSTALL @@ -0,0 +1,368 @@ +Installation Instructions +************************* + + Copyright (C) 1994-1996, 1999-2002, 2004-2016 Free Software +Foundation, Inc. + + Copying and distribution of this file, with or without modification, +are permitted in any medium without royalty provided the copyright +notice and this notice are preserved. This file is offered as-is, +without warranty of any kind. + +Basic Installation +================== + + Briefly, the shell command './configure && make && make install' +should configure, build, and install this package. The following +more-detailed instructions are generic; see the 'README' file for +instructions specific to this package. Some packages provide this +'INSTALL' file but do not implement all of the features documented +below. 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Until the limitation is lifted, you can use this +workaround: + + CONFIG_SHELL=/bin/bash ./configure CONFIG_SHELL=/bin/bash + +'configure' Invocation +====================== + + 'configure' recognizes the following options to control how it +operates. + +'--help' +'-h' + Print a summary of all of the options to 'configure', and exit. + +'--help=short' +'--help=recursive' + Print a summary of the options unique to this package's + 'configure', and exit. The 'short' variant lists options used only + in the top level, while the 'recursive' variant lists options also + present in any nested packages. + +'--version' +'-V' + Print the version of Autoconf used to generate the 'configure' + script, and exit. + +'--cache-file=FILE' + Enable the cache: use and save the results of the tests in FILE, + traditionally 'config.cache'. FILE defaults to '/dev/null' to + disable caching. + +'--config-cache' +'-C' + Alias for '--cache-file=config.cache'. + +'--quiet' +'--silent' +'-q' + Do not print messages saying which checks are being made. To + suppress all normal output, redirect it to '/dev/null' (any error + messages will still be shown). + +'--srcdir=DIR' + Look for the package's source code in directory DIR. Usually + 'configure' can determine that directory automatically. + +'--prefix=DIR' + Use DIR as the installation prefix. *note Installation Names:: for + more details, including other options available for fine-tuning the + installation locations. + +'--no-create' +'-n' + Run the configure checks, but stop before creating any output + files. + +'configure' also accepts some other, not widely useful, options. Run +'configure --help' for more details. diff --git a/Makefile.am b/Makefile.am new file mode 100644 index 0000000..168da9d --- /dev/null +++ b/Makefile.am @@ -0,0 +1 @@ +SUBDIRS=graph diff --git a/NEWS b/NEWS new file mode 100644 index 0000000..a90f682 --- /dev/null +++ b/NEWS @@ -0,0 +1 @@ +TODO: Announce news here. \ No newline at end of file diff --git a/README b/README new file mode 100644 index 0000000..f73834f --- /dev/null +++ b/README @@ -0,0 +1,3 @@ +This is a parser generator to be used as an Emacs dynamic package. + +TODO: Provide more details. \ No newline at end of file diff --git a/THANKS b/THANKS new file mode 100644 index 0000000..e69de29 diff --git a/benches/bench_receme.rs b/benches/bench_receme.rs new file mode 100644 index 0000000..c9583a9 --- /dev/null +++ b/benches/bench_receme.rs @@ -0,0 +1,293 @@ +use criterion::{black_box, criterion_group, criterion_main, Criterion}; + +use receme::{ + catana::{Ana, Cata}, + functor::Functor, + hylo::Hylo, + tree::{DFTree, TEStrategy, Tree, TreeIndex}, +}; + +#[derive(Debug, Clone)] +enum Expr { + Add(T, T), + Lit(isize), +} + +impl Functor for Expr { + type Target = Expr; + + fn fmap(self, mut f: impl FnMut(T) -> S) -> Self::Target { + match self { + Expr::Add(a, b) => Expr::Add(f(a), f(b)), + Expr::Lit(value) => Expr::Lit(value), + } + } +} + +#[derive(Debug, Clone)] +enum ExBox { + Add(Box, Box), + Lit(isize), +} + +impl ExBox { + fn lit(value: isize) -> Self { + Self::Lit(value) + } + + fn add(a: ExBox, b: ExBox) -> Self { + Self::Add(Box::new(a), Box::new(b)) + } +} + +pub fn bench(c: &mut Criterion) { + fn construct_tree() -> Tree> { + let strategy: TEStrategy = TEStrategy::UnsafeArena; + + let elements: Vec> = vec![ + Expr::Add(1, 2).fmap(TreeIndex::new), + Expr::Lit(1), + Expr::Add(3, 4).fmap(TreeIndex::new), + Expr::Lit(3), + Expr::Add(5, 6).fmap(TreeIndex::new), + Expr::Lit(10), + Expr::Lit(-14), + ]; + + Tree::new(elements, strategy) + } + + fn construct_box_tree() -> Box { + Box::new(ExBox::add( + ExBox::lit(1), + ExBox::add(ExBox::lit(3), ExBox::add(ExBox::lit(10), ExBox::lit(-14))), + )) + } + + let tree = construct_tree(); + + let safe_tree = { + let mut tree = tree.clone(); + tree.set_strategy(Default::default()); + tree + }; + + let depth_first_tree = { + let mut tree = tree.clone(); + tree.set_strategy(TEStrategy::DepthFirst); + tree + }; + + let boxtree = construct_box_tree(); + + c.bench_function("bench cata", |b| { + b.iter(|| { + let result = tree.clone().cata(|expr: Expr| match expr { + Expr::Add(a, b) => a + b, + Expr::Lit(v) => v, + }); + + black_box(result); + }) + }); + + c.bench_function("bench cata safe", |b| { + b.iter(|| { + let result = safe_tree.clone().cata(|expr: Expr| match expr { + Expr::Add(a, b) => a + b, + Expr::Lit(v) => v, + }); + + black_box(result); + }) + }); + + c.bench_function("bench cata depth first", |b| { + b.iter(|| { + let result = depth_first_tree + .clone() + .cata(|expr: Expr| match expr { + Expr::Add(a, b) => a + b, + Expr::Lit(v) => v, + }); + + black_box(result); + }) + }); + + c.bench_function("bench cata loop", |b| { + b.iter(|| { + let tree = tree.clone(); + + let mut stack: Vec> = vec![Ok(0)]; + let mut result_stack: Vec = vec![]; + + while let Some(top) = stack.pop() { + let top_is_ok_p = top.is_ok(); + + let top = match top { + Ok(top) => top, + Err(top) => top, + }; + + let top_node = tree.nth(top).unwrap(); + + match top_node { + Expr::Add(a, b) => { + if top_is_ok_p { + stack.push(Err(top)); + stack.push(Ok(**b)); + stack.push(Ok(**a)); + } else { + let a = result_stack.pop().unwrap(); + let b = result_stack.pop().unwrap(); + + result_stack.push(a + b); + } + } + Expr::Lit(v) => result_stack.push(*v), + } + } + + let result = result_stack.pop().unwrap(); + + black_box(result); + }) + }); + + c.bench_function("bench ana box loop", |b| { + b.iter(|| { + let boxtree = boxtree.clone(); + + let mut elements = vec![]; + + let mut stack = vec![boxtree]; + + while let Some(bt) = stack.pop() { + match *bt { + ExBox::Add(a, b) => { + let len = elements.len(); + + elements.push(Expr::Add(TreeIndex::new(len + 1), TreeIndex::new(len + 2))); + + stack.push(b); + stack.push(a); + } + ExBox::Lit(v) => elements.push(Expr::Lit(v)), + } + } + + let tree: Tree> = Tree::new(elements, Default::default()); + + black_box(tree); + }) + }); + + c.bench_function("bench ana boxed", |b| { + b.iter(|| { + let boxtree = boxtree.clone(); + + let tree = Tree::ana(boxtree, |bt: Box| match *bt { + ExBox::Add(a, b) => Expr::Add(a, b), + ExBox::Lit(v) => Expr::Lit(v), + }); + + black_box(tree); + }) + }); + + c.bench_function("bench ana depth first boxed", |b| { + b.iter(|| { + let boxtree = boxtree.clone(); + + let tree = DFTree::ana(boxtree, |bt: Box| match *bt { + ExBox::Add(a, b) => Expr::Add(a, b), + ExBox::Lit(v) => Expr::Lit(v), + }); + + black_box(tree); + }) + }); + + c.bench_function("bench hylo", |b| { + b.iter(|| { + let boxtree = boxtree.clone(); + + black_box(Tree::hylo( + boxtree, + |expr| match expr { + Expr::Add(a, b) => a + b, + Expr::Lit(v) => v, + }, + |bt: Box| match *bt { + ExBox::Add(a, b) => Expr::Add(a, b), + ExBox::Lit(v) => Expr::Lit(v), + }, + )) + }) + }); + + c.bench_function("bench hylo loop", |b| { + b.iter(|| { + let boxtree = boxtree.clone(); + + let mut elements = vec![]; + + let mut stack = vec![boxtree]; + + while let Some(bt) = stack.pop() { + match *bt { + ExBox::Add(a, b) => { + let len = elements.len(); + + elements.push(Expr::Add(TreeIndex::new(len + 1), TreeIndex::new(len + 2))); + + stack.push(b); + stack.push(a); + } + ExBox::Lit(v) => elements.push(Expr::Lit(v)), + } + } + + let tree: Tree> = Tree::new(elements, Default::default()); + + let mut stack: Vec> = vec![Ok(0)]; + let mut result_stack: Vec = vec![]; + + while let Some(top) = stack.pop() { + let top_is_ok_p = top.is_ok(); + let top = match top { + Ok(top) => top, + Err(top) => top, + }; + + let top_node = tree.nth(top).unwrap(); + + match top_node { + Expr::Add(a, b) => { + if top_is_ok_p { + stack.push(Err(top)); + stack.push(Ok(**b)); + stack.push(Ok(**a)); + } else { + let a = result_stack.pop().unwrap(); + let b = result_stack.pop().unwrap(); + + result_stack.push(a + b); + } + } + Expr::Lit(v) => result_stack.push(*v), + } + } + + let result = result_stack.pop().unwrap(); + + assert_eq!(result, 0); + + black_box(result); + }) + }); +} + +criterion_group!(benches, bench); +criterion_main!(benches); diff --git a/configure.ac b/configure.ac new file mode 100644 index 0000000..fbf987e --- /dev/null +++ b/configure.ac @@ -0,0 +1,28 @@ +AC_PREREQ([2.60]) + +AC_INIT([REP], m4_esyscmd([./find-version.sh]), [durand@jsdurand.xyz]) + +dnl patsubst(m4_esyscmd([./find-version.sh]), ` "') + +AC_COPYRIGHT([This package is covered by GPL v3.]) + +AC_CONFIG_AUX_DIR([build-aux]) + +AM_INIT_AUTOMAKE([subdir-objects]) + +AM_SILENT_RULES([yes]) + +dnl AC_CONFIG_SUBDIRS([graph], [receme], [nfa], [repcore]) +dnl AC_CONFIG_SUBDIRS([graph]) + +AC_PATH_PROG([CARGO], [cargo], [notfound]) +AS_IF([test "$CARGO" = "notfound"], [AC_MSG_ERROR([cargo is required])]) + +AC_PATH_PROG([RUSTC], [rustc], [notfound]) +AS_IF([test "$RUSTC" = "notfound"], [AC_MSG_ERROR([rustc is required])]) + +AC_CONFIG_FILES([Makefile graph/Makefile]) + +AC_OUTPUT + + diff --git a/find-version.sh b/find-version.sh new file mode 100755 index 0000000..4ac390e --- /dev/null +++ b/find-version.sh @@ -0,0 +1,20 @@ +#!/bin/sh +":"; exec emacs --quick --script "$0" -- "$@" # -*- mode: emacs-lisp; lexical-binding: t; -*- + +(with-temp-buffer + (insert-file-contents "Cargo.toml") + (goto-char (point-min)) + (cond + ((search-forward "version =" nil t) + (re-search-forward " *" (line-end-position) t) + (cond + ((= (char-after) 34)) + ((error "Invalid syntax at %d" (point)))) + (let ((end (line-end-position))) + (cond + ((= (char-before end) 34)) + ((error "Invalid syntax at %d" (1- end)))) + (princ + (buffer-substring-no-properties + (1+ (point)) (1- end))))) + ((print "Unknown")))) diff --git a/graph/Cargo.toml b/graph/Cargo.toml new file mode 100644 index 0000000..d8f0622 --- /dev/null +++ b/graph/Cargo.toml @@ -0,0 +1,12 @@ +[package] +name = "graph" +version = "0.1.0" +edition = "2021" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] + +[features] + + diff --git a/graph/Makefile.am b/graph/Makefile.am new file mode 100644 index 0000000..776b911 --- /dev/null +++ b/graph/Makefile.am @@ -0,0 +1,12 @@ +.PHONY: dev rel + +all: dev + +dev: + @CARGO@ build + +rel: + @CARGO@ build --release + +clean: + @CARGO@ clean diff --git a/graph/src/adlist.rs b/graph/src/adlist.rs new file mode 100644 index 0000000..c16ceb2 --- /dev/null +++ b/graph/src/adlist.rs @@ -0,0 +1,181 @@ +#![warn(missing_docs)] +//! This file implements a data type that implements the trait +//! [`Graph`][super::Graph]. This data type represents graphs using +//! adjacency lists internally. + +use super::{ExtGraph, Graph}; +use crate::error::Error; + +// #[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd)] +// struct ALEdge { +// to: usize, +// } + +// impl ALEdge { +// fn new(to: usize) -> Self { +// Self { to } +// } +// } + +#[derive(Debug, Clone, Default)] +struct ALNode { + children: Vec, +} + +impl ALNode { + fn new(children: Vec) -> Self { + Self { children } + } +} + +/// The graph implemented using adjacency lists. +#[derive(Debug, Clone, Default)] +pub struct ALGraph { + nodes: Vec, +} + +impl Graph for ALGraph { + type Iter<'a> = std::iter::Copied>; + + #[inline] + fn is_empty(&self) -> bool { + self.nodes.is_empty() + } + + #[inline] + fn nodes_len(&self) -> usize { + self.nodes.len() + } + + #[inline] + fn children_of(&self, node_id: usize) -> Result, Error> { + match self.nodes.get(node_id) { + Some(node) => Ok(node.children.iter().copied()), + None => Err(Error::IndexOutOfBounds(node_id, self.nodes_len())), + } + } + + #[inline] + fn degree(&self, node_id: usize) -> Result { + match self.nodes.get(node_id) { + Some(node) => Ok(node.children.len()), + None => Err(Error::IndexOutOfBounds(node_id, self.nodes_len())), + } + } + + #[inline] + fn is_empty_node(&self, node_id: usize) -> Result { + match self.nodes.get(node_id) { + Some(node) => Ok(node.children.is_empty()), + None => Err(Error::IndexOutOfBounds(node_id, self.nodes_len())), + } + } + + fn has_edge(&self, source: usize, target: usize) -> Result { + if !self.has_node(source) { + Err(Error::IndexOutOfBounds(source, self.nodes_len())) + } else if !self.has_node(target) { + Err(Error::IndexOutOfBounds(target, self.nodes_len())) + } else { + Ok(self.nodes.get(source).unwrap().children.contains(&target)) + } + } +} + +impl ExtGraph for ALGraph { + fn extend(&mut self, edges: impl IntoIterator) -> Result { + let mut new_node_children = Vec::new(); + + for edge_to in edges.into_iter() { + if !self.has_node(edge_to) { + return Err(Error::IndexOutOfBounds(edge_to, self.nodes_len())); + } + + new_node_children.push(edge_to); + } + + let new_node = ALNode::new(new_node_children); + + self.nodes.push(new_node); + + Ok(self.nodes.len() - 1) + } +} + +#[cfg(test)] +mod algraph_test { + use super::*; + + #[test] + fn test_graph_apis() -> Result<(), Error> { + let mut graph = ALGraph::default(); + + assert!(graph.is_empty()); + + graph.extend(std::iter::empty())?; + + graph.extend([0].iter().copied())?; + graph.extend([0, 1].iter().copied())?; + graph.extend([0, 2].iter().copied())?; + graph.extend([1, 2].iter().copied())?; + graph.extend([1, 2, 3].iter().copied())?; + + let graph = graph; + + assert_eq!(graph.nodes_len(), 6); + + assert_eq!(graph.children_of(5)?.collect::>(), vec![1, 2, 3]); + + assert_eq!(graph.degree(4)?, 2); + + assert!(graph.is_empty_node(0)?); + assert!(!graph.is_empty_node(1)?); + + assert!(graph.has_edge(3, 2)?); + assert!(!graph.has_edge(3, 1)?); + assert_eq!(graph.has_edge(3, 6), Err(Error::IndexOutOfBounds(6, 6))); + + Ok(()) + } + + #[test] + fn test_extending_algraph_normal() -> Result<(), Error> { + let mut graph = ALGraph::default(); + + let new = graph.extend(std::iter::empty())?; + + println!("new index = {new}"); + + println!("new graph = {graph:?}"); + + let new = graph.extend([0].iter().copied())?; + + println!("new index = {new}"); + + println!("new graph = {graph:?}"); + + let new = graph.extend([0, 1].iter().copied())?; + + println!("new index = {new}"); + + println!("new graph = {graph:?}"); + + Ok(()) + } + + #[test] + fn test_extending_algraph_error() -> Result<(), Error> { + let mut graph = ALGraph::default(); + + graph.extend(std::iter::empty())?; + + graph.extend([0].iter().copied())?; + + assert_eq!( + graph.extend([2].iter().copied()), + Err(Error::IndexOutOfBounds(2, 2)) + ); + + Ok(()) + } +} diff --git a/graph/src/adset.rs b/graph/src/adset.rs new file mode 100644 index 0000000..58fed4c --- /dev/null +++ b/graph/src/adset.rs @@ -0,0 +1,229 @@ +#![warn(missing_docs)] +//! This file implements a data type that implements the trait +//! [`Graph`][super::Graph]. This data type represents graphs using +//! adjacency sets internally. +//! +//! I need this because the derivatives languages should not allow +//! duplications of languages, so it is more convenient if the +//! underlying graph type **cannot** represent duplicate edges. + +use super::{ExtGraph, Graph}; +use crate::error::Error; + +// If one wants to use another implementation for a set, import that +// as Set, and nothing else needs to be changed, ideally. +use std::collections::{hash_set::Iter, HashSet as Set}; + +#[derive(Debug, Copy, Clone, Eq, PartialEq, Ord, PartialOrd, Hash)] +struct ASEdge { + to: usize, +} + +impl ASEdge { + fn new(to: usize) -> Self { + Self { to } + } +} + +#[derive(Debug, Clone, Default)] +struct ASNode { + children: Set, +} + +impl ASNode { + fn new(children: Set) -> Self { + Self { children } + } +} + +/// The graph implemented using adjacency sets. +#[derive(Debug, Clone, Default)] +pub struct ASGraph { + nodes: Vec, +} + +/// A delegation of iterators. +/// +/// This is here to avoid using a boxed pointer, in order to save some +/// allocations. +pub struct ASIter<'a> { + iter: Iter<'a, ASEdge>, +} + +impl<'a> Iterator for ASIter<'a> { + type Item = usize; + + fn next(&mut self) -> Option { + self.iter.next().map(|edge| edge.to) + } + + fn size_hint(&self) -> (usize, Option) { + self.iter.size_hint() + } +} + +impl<'a> ExactSizeIterator for ASIter<'a> { + fn len(&self) -> usize { + self.iter.len() + } +} + +impl Graph for ASGraph { + type Iter<'a> = ASIter<'a>; + + #[inline] + fn is_empty(&self) -> bool { + self.nodes.is_empty() + } + + #[inline] + fn nodes_len(&self) -> usize { + self.nodes.len() + } + + fn children_of(&self, node_id: usize) -> Result, Error> { + match self.nodes.get(node_id) { + Some(node) => { + let iter = node.children.iter(); + Ok(Self::Iter { iter }) + } + None => Err(Error::IndexOutOfBounds(node_id, self.nodes_len())), + } + } + + #[inline] + fn degree(&self, node_id: usize) -> Result { + match self.nodes.get(node_id) { + Some(node) => Ok(node.children.len()), + None => Err(Error::IndexOutOfBounds(node_id, self.nodes_len())), + } + } + + #[inline] + fn is_empty_node(&self, node_id: usize) -> Result { + match self.nodes.get(node_id) { + Some(node) => Ok(node.children.is_empty()), + None => Err(Error::IndexOutOfBounds(node_id, self.nodes_len())), + } + } + + #[inline] + fn has_edge(&self, source: usize, target: usize) -> Result { + if !self.has_node(source) { + Err(Error::IndexOutOfBounds(source, self.nodes_len())) + } else if !self.has_node(target) { + Err(Error::IndexOutOfBounds(target, self.nodes_len())) + } else { + Ok(self + .nodes + .get(source) + .unwrap() + .children + .contains(&ASEdge::new(target))) + } + } +} + +impl ExtGraph for ASGraph { + fn extend(&mut self, edges: impl IntoIterator) -> Result { + let mut new_node_children = Set::default(); + + for edge_to in edges.into_iter() { + if !self.has_node(edge_to) { + return Err(Error::IndexOutOfBounds(edge_to, self.nodes_len())); + } + + new_node_children.insert(ASEdge::new(edge_to)); + } + + let new_node = ASNode::new(new_node_children); + + self.nodes.push(new_node); + + Ok(self.nodes.len() - 1) + } +} + +#[cfg(test)] +mod asgraph_test { + use super::*; + + #[test] + fn test_graph_apis() -> Result<(), Error> { + let mut graph = ASGraph::default(); + + assert!(graph.is_empty()); + + graph.extend(std::iter::empty())?; + + graph.extend([0].iter().copied())?; + graph.extend([0, 1].iter().copied())?; + graph.extend([0, 2].iter().copied())?; + graph.extend([1, 2].iter().copied())?; + graph.extend([1, 2, 3].iter().copied())?; + + let graph = graph; + + assert_eq!(graph.nodes_len(), 6); + + assert_eq!(graph.children_of(5)?.collect::>(), { + let mut set = Set::default(); + set.insert(1); + set.insert(3); + set.insert(2); + set + }); + + assert_eq!(graph.degree(4)?, 2); + + assert!(graph.is_empty_node(0)?); + assert!(!graph.is_empty_node(1)?); + + assert!(graph.has_edge(3, 2)?); + assert!(!graph.has_edge(3, 1)?); + assert_eq!(graph.has_edge(3, 6), Err(Error::IndexOutOfBounds(6, 6))); + + Ok(()) + } + + #[test] + fn test_extending_algraph_normal() -> Result<(), Error> { + let mut graph = ASGraph::default(); + + let new = graph.extend(std::iter::empty())?; + + println!("new index = {new}"); + + println!("new graph = {graph:?}"); + + let new = graph.extend([0].iter().copied())?; + + println!("new index = {new}"); + + println!("new graph = {graph:?}"); + + let new = graph.extend([0, 1].iter().copied())?; + + println!("new index = {new}"); + + println!("new graph = {graph:?}"); + + Ok(()) + } + + #[test] + fn test_extending_algraph_error() -> Result<(), Error> { + let mut graph = ASGraph::default(); + + graph.extend(std::iter::empty())?; + + graph.extend([0].iter().copied())?; + + assert_eq!( + graph.extend([2].iter().copied()), + Err(Error::IndexOutOfBounds(2, 2)) + ); + + Ok(()) + } +} diff --git a/graph/src/error.rs b/graph/src/error.rs new file mode 100644 index 0000000..2162685 --- /dev/null +++ b/graph/src/error.rs @@ -0,0 +1,26 @@ +#![warn(missing_docs)] +//! This file implements the error data type of the graph library. + +use std::fmt::{self, Display}; + +/// The error type for methods of the trait [`Graph`][`super::Graph`]. +#[derive(Debug, Clone, PartialEq, Eq, Ord, PartialOrd)] +pub enum Error { + /// The index is out of bounds. + /// + /// The first component is the index that is out of bounds, and + /// the second component is the current length of nodes. + IndexOutOfBounds(usize, usize), +} + +impl Display for Error { + fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { + match self { + Error::IndexOutOfBounds(index, len) => { + write!(f, "index {index} out of bounds {len} ") + } + } + } +} + +impl std::error::Error for Error {} diff --git a/graph/src/labelled.rs b/graph/src/labelled.rs new file mode 100644 index 0000000..1cb2461 --- /dev/null +++ b/graph/src/labelled.rs @@ -0,0 +1,426 @@ +#![warn(missing_docs)] +//! This file implements a labelled graph. See the +//! [trait][super::LabelGraph] for details. +//! +//! Since the method +//! [`find_children_with_label`][super::LabelGraph::find_children_with_label] +//! needs to be implemented efficiently, we store the mappings between +//! labels and edges in both directions. + +#[allow(unused_imports)] +use super::{Graph, GraphLabel, LabelExtGraph, LabelGraph}; +#[allow(unused_imports)] +use crate::error::Error; + +// We use BTreeMap and BTreeSet here as we need to exclude duplicate +// edge sets, while an ordinary hashmap and hashset do not allow +// hashing. +use std::collections::{ + btree_map::{Iter as MapIter, Keys}, + btree_set::Iter, + BTreeMap as Map, BTreeSet as Set, HashMap as HMap, +}; + +#[derive(Debug, Clone, Default)] +struct DLNode { + by_target: Map>, + by_label: Map>, + flat: Vec<(T, usize)>, +} + +impl DLNode { + fn new( + by_target: Map>, + by_label: Map>, + flat: Vec<(T, usize)>, + ) -> Self { + Self { + by_target, + by_label, + flat, + } + } +} + +/// Mapping a set of edges to an index of node. +type EdgeMap = HMap, usize>; + +/// Double direction Labelled Graph. +/// +/// Each node is supposed to have a unique edge set. Constructing +/// methods such as from the trait +/// [`LabelExtGraph`][super::LabelExtGraph] already handles the +/// elimination of duplication. +#[derive(Debug, Clone)] +pub struct DLGraph { + nodes: Vec>, + edges_table: EdgeMap, +} + +impl DLGraph { + #[inline] + /// Return an empty graph. + pub fn new() -> Self { + Self { + nodes: Vec::new(), + edges_table: HMap::default(), + } + } +} + +impl Default for DLGraph { + #[inline] + fn default() -> Self { + Self::new() + } +} + +impl Graph for DLGraph { + // Not using a boxed pointer is supposed to save some allocations. + type Iter<'a> = std::iter::Copied>> where T: 'a; + + #[inline] + fn is_empty(&self) -> bool { + self.nodes.is_empty() + } + + #[inline] + fn nodes_len(&self) -> usize { + self.nodes.len() + } + + #[inline] + fn children_of(&self, node_id: usize) -> Result, Error> { + match self.nodes.get(node_id) { + Some(node) => Ok(node.by_target.keys().copied()), + None => Err(Error::IndexOutOfBounds(node_id, self.nodes.len())), + } + } + + #[inline] + /// Return the number of "children" of a node, or an error if the + /// node is not a member of the graph. + /// + /// This counts edges with different labels as different edges. + fn degree(&self, node_id: usize) -> Result { + self.nodes + .get(node_id) + .ok_or(Error::IndexOutOfBounds(node_id, self.nodes.len())) + .map(|node| node.flat.len()) + } + + #[inline] + fn is_empty_node(&self, node_id: usize) -> Result { + self.nodes + .get(node_id) + .ok_or(Error::IndexOutOfBounds(node_id, self.nodes.len())) + .map(|node| node.flat.is_empty()) + } + + fn has_edge(&self, source: usize, target: usize) -> Result { + match self.nodes.get(source) { + Some(source_node) => { + if self.nodes.get(target).is_none() { + return Err(Error::IndexOutOfBounds(target, self.nodes.len())); + } + + Ok(source_node.by_target.contains_key(&target)) + } + None => Err(Error::IndexOutOfBounds(source, self.nodes.len())), + } + } +} + +/// A delegation of iterators. +/// +/// This is used to avoid a boxed pointer to an iterator. +#[derive(Default, Debug)] +pub struct LabelIndexIter<'a> { + iter: Option>>, +} + +impl<'a> Iterator for LabelIndexIter<'a> { + type Item = usize; + + #[inline] + fn next(&mut self) -> Option { + self.iter.as_mut().map(|iterator| iterator.next()).flatten() + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + match &self.iter { + Some(iter) => iter.size_hint(), + None => (0, Some(0)), + } + } +} + +impl<'a> ExactSizeIterator for LabelIndexIter<'a> { + #[inline] + fn len(&self) -> usize { + match &self.iter { + Some(iter) => iter.len(), + None => 0, + } + } +} + +impl<'a> LabelIndexIter<'a> { + fn new(iter: std::iter::Copied>) -> Self { + let iter = Some(iter); + Self { iter } + } +} + +// A convenience method +impl<'a> From<&'a Set> for LabelIndexIter<'a> { + fn from(set: &'a Set) -> Self { + Self::new(set.iter().copied()) + } +} + +#[derive(Debug)] +/// A delegation of iterators. +/// +/// This is used to avoid a boxed pointer to an iterator. +pub struct LabelIter<'a, T> { + iter: MapIter<'a, T, Set>, +} + +impl<'a, T> ExactSizeIterator for LabelIter<'a, T> { + #[inline] + fn len(&self) -> usize { + self.iter.len() + } +} + +impl<'a, T> LabelIter<'a, T> { + fn new(iter: MapIter<'a, T, Set>) -> Self { + Self { iter } + } +} + +impl<'a, T> Iterator for LabelIter<'a, T> { + type Item = (&'a T, LabelIndexIter<'a>); + + #[inline] + fn next(&mut self) -> Option { + self.iter.next().map(|(label, set)| (label, set.into())) + } + + #[inline] + fn size_hint(&self) -> (usize, Option) { + self.iter.size_hint() + } +} + +impl LabelGraph for DLGraph { + type Iter<'a> = LabelIndexIter<'a> where T: 'a; + + type LabelIter<'a> = LabelIter<'a,T> where T: 'a; + + fn edge_label(&self, source: usize, target: usize) -> Result, Error> { + if self.has_edge(source, target)? { + Ok(self + .nodes + .get(source) + .unwrap() + .by_target + .get(&target) + .unwrap() + .iter() + .copied() + .collect()) + } else { + Ok(Vec::new()) + } + } + + fn find_children_with_label( + &self, + node_id: usize, + label: &T, + ) -> Result<>::Iter<'_>, Error> { + match self + .nodes + .get(node_id) + .ok_or(Error::IndexOutOfBounds(node_id, self.nodes.len()))? + .by_label + .get(label) + { + Some(set) => Ok(set.into()), + None => Ok(Default::default()), + } + } + + #[inline] + fn labels_of(&self, node_id: usize) -> Result, Error> { + match self.nodes.get(node_id) { + Some(node) => Ok(Self::LabelIter::new(node.by_label.iter())), + None => Err(Error::IndexOutOfBounds(node_id, self.nodes.len())), + } + } +} + +impl LabelExtGraph for DLGraph { + fn extend(&mut self, edges: impl IntoIterator) -> Result { + let mut by_target: Map> = Map::default(); + let mut by_label: Map> = Map::default(); + let mut flat = Vec::new(); + let mut edges_set = Set::new(); + + for (label, to) in edges { + if !self.has_node(to) { + return Err(Error::IndexOutOfBounds(to, self.nodes.len())); + } + + edges_set.insert((label, to)); + + if let Some(set) = by_target.get(&to) { + if !set.contains(&label) { + flat.push((label, to)); + by_target.get_mut(&to).unwrap().insert(label); + by_label + .entry(label) + .or_insert_with(Default::default) + .insert(to); + } + } else { + flat.push((label, to)); + by_target + .entry(to) + .or_insert_with(Default::default) + .insert(label); + by_label + .entry(label) + .or_insert_with(Default::default) + .insert(to); + } + } + + match self.edges_table.get(&edges_set) { + Some(old_index) => Ok(*old_index), + None => { + let new_node = DLNode::new(by_target, by_label, flat); + let new_index = self.nodes_len(); + + self.edges_table.insert(edges_set, new_index); + + self.nodes.push(new_node); + + Ok(new_index) + } + } + } +} + +#[cfg(test)] +mod label_test { + use super::*; + + macro_rules! set { + () => { Set::::default() }; + ($($num:literal),*) => { + { + let mut set: Set = Set::default(); + $(set.insert($num);)* + set + } + }; + } + + macro_rules! map { + () => { Map::>::default() }; + ($(($key:literal, $value:expr)),*) => { + { + let mut map: Map> = Map::default(); + $(map.insert($key, $value);)* + map + } + }; + } + + #[test] + fn test_graph_apis() -> Result<(), Error> { + let mut graph: DLGraph = Default::default(); + + // testing empty graph + assert!(graph.is_empty()); + + // testing adding an empty node + assert_eq!(graph.extend(std::iter::empty())?, 0); + + // testing nodes_len + assert_eq!(graph.nodes_len(), 1); + + // testing extension + + assert_eq!(graph.extend([(0, 0)].iter().copied())?, 1); + assert_eq!(graph.extend([(1, 0), (1, 1)].iter().copied())?, 2); + assert_eq!(graph.extend([(3, 0), (3, 2)].iter().copied())?, 3); + assert_eq!(graph.extend([(1, 1), (1, 2)].iter().copied())?, 4); + assert_eq!(graph.extend([(2, 1), (3, 2), (2, 3)].iter().copied())?, 5); + + // testing adding a duplicated edge set + assert_eq!(graph.extend([(2, 1), (2, 3), (3, 2)].iter().copied())?, 5); + assert_eq!(graph.extend([(3, 2), (3, 0)].iter().copied())?, 3); + + let graph = graph; + + // ensuring the correct length + assert_eq!(graph.nodes_len(), 6); + + // testing children_of + assert_eq!(graph.children_of(5)?.collect::>(), set!(1, 3, 2)); + + // testing find_children_with_label + assert_eq!( + graph.find_children_with_label(5, &2)?.collect::>(), + set!(1, 3) + ); + + // testing edge_label + assert_eq!( + graph.edge_label(5, 2)?.into_iter().collect::>(), + set!(3) + ); + assert!(matches!( + graph.edge_label(6, 2), + Err(Error::IndexOutOfBounds(6, 6)) + )); + + // testing degree + assert_eq!(graph.degree(4)?, 2); + + // testing is_empty_node + assert!(graph.is_empty_node(0)?); + assert!(!graph.is_empty_node(1)?); + + // testing has_edge + assert!(graph.has_edge(3, 2)?); + assert!(!graph.has_edge(3, 1)?); + assert!(matches!( + graph.has_edge(3, 6), + Err(Error::IndexOutOfBounds(6, 6)) + )); + + // testing labels_of + let mut label_map: Map> = Map::default(); + + for (label, children) in graph.labels_of(5)? { + label_map.insert(*label, children.collect()); + } + + let compare_map = map!((2, set!(1, 3)), (3, set!(2))); + + assert_eq!(label_map, compare_map); + + assert!(matches!( + graph.labels_of(6), + Err(Error::IndexOutOfBounds(6, 6)) + )); + + Ok(()) + } +} diff --git a/graph/src/lib.rs b/graph/src/lib.rs new file mode 100644 index 0000000..7b74ee1 --- /dev/null +++ b/graph/src/lib.rs @@ -0,0 +1,203 @@ +#![warn(missing_docs)] +//! This crate implements a trait API for graphs that the crate "rep" +//! needs. +//! +//! Also a default implementation for the trait is provided, so that +//! by default no external crates are needed, whereas it is easy to +//! use external crates, if so derired. + +use std::hash::Hash; + +pub mod error; + +pub mod adset; + +pub use adset::ASGraph; + +pub mod adlist; + +pub use adlist::ALGraph; + +pub mod labelled; + +pub use labelled::DLGraph; + +use error::Error; + +/// The expected behaviour of an immutable graph. +pub trait Graph: Default { + /// A type that iterates through the node indices. + type Iter<'a>: Iterator + 'a + where + Self: 'a; + + /// Return true if and only if the graph has no nodes. + fn is_empty(&self) -> bool; + + /// Return the length of nodes in the graph. + fn nodes_len(&self) -> usize; + + #[inline] + /// Return the length of edges in the graph. + /// + /// This is optional. Implementations need not support this. + fn edges_len(&self) -> Option { + None + } + + #[inline] + /// Return an iterator of nodes represented as unsigned integers. + /// + /// If a custom application needs to have labels on nodes, just + /// associate the label to the node internally, and define an + /// extension trait that allows querying those additional labels. + /// + /// This design choice is based on the idea that this library + /// should be minimal and only provide the core of a graph. As a + /// label is not really core, it is not included here. + fn nodes(&self) -> Box + '_> { + Box::new(0..self.nodes_len()) + } + + /// Return an iterator of edges going out of a node. + /// + /// Return an error if the node is not known to the graph. + fn children_of(&self, node_id: usize) -> Result, Error>; + + #[inline] + /// Return an iterator of edges represented as pairs (FROM, TO). + /// + /// The default implementation iterates through the nodes and then + /// iterates through their children. If the implementation has a + /// more efficient method, overwrite this method. + fn edges(&self) -> Box + '_> { + Box::new(self.nodes().flat_map(|node| { + self.children_of(node) + // If this node is invalid, this means the + // implementation of `nodes` is wrong, so it is + // appropriate to panic here. + .unwrap() + .map(move |child| (node, child)) + })) + } + + #[inline] + /// Return true if and only if the node is in the graph. + fn has_node(&self, node_id: usize) -> bool { + (0..self.nodes_len()).contains(&node_id) + } + + /// Return the number of "children" of a node, or an error if the + /// node is not a member of the graph. + fn degree(&self, node_id: usize) -> Result; + + /// Return a boolean indicating if the node has no children, or an + /// error if the node is not a member of the graph. + fn is_empty_node(&self, node_id: usize) -> Result; + + /// Return true if and only if there is an edge from the source to + /// the target. + /// + /// Return an error if either the source or the target is an + /// invalid node. + fn has_edge(&self, source: usize, target: usize) -> Result; +} + +/// A graph that can be extended, but not mutated, in the sense that +/// existing nodes and edges will not be modified nor removed, but new +/// nodes can be added. The index of the new node will be returned. +/// +/// Implementations can choose to keep a set of sets of edges, so that +/// new nodes will not have duplicate edge sets. In this case, the +/// returned new node index is not necessarily equal to +/// self.nodes_len() - 1, and hence the return type is designed in +/// this way. +pub trait ExtGraph: Graph { + /// Add a new node with `edges`. + /// + /// If an edge from `edges` points to a non-existent node, return + /// an error. + fn extend(&mut self, edges: impl IntoIterator) -> Result; +} + +/// The type of labels should be comparable and hashable. +pub trait GraphLabel: Hash + Eq + PartialEq + Clone + Copy + Ord + PartialOrd {} + +impl GraphLabel for T {} + +/// A labelled graph is just a graph with labels associated to +/// vertices and / or edges. +/// +/// This trait defines what the package needs out of a labelled graph. +/// +/// Any implementation should be able to handle a set of types for +/// labels, so this trait is generic over the label type. +pub trait LabelGraph: Graph { + /// A type that iterates through the node indices. + type Iter<'a>: Iterator + 'a + where + Self: 'a; + + /// A type that iterates through labels. + type LabelIter<'a>: Iterator>::Iter<'a>)> + 'a + where + Self: 'a, + T: 'a; + + #[inline] + /// Return the label of a vertex or an error if the node is + /// invalid. + /// + /// The default implementation always returns None for a valid + /// node. + fn vertex_label(&self, node_id: usize) -> Result, Error> { + if self.has_node(node_id) { + Ok(None) + } else { + Err(Error::IndexOutOfBounds(node_id, self.nodes_len())) + } + } + + #[inline] + /// Return the label of an edge or an error if some node is + /// invalid. + /// + /// The default implementation always returns an empty vector for + /// valid nodes. + fn edge_label(&self, source: usize, target: usize) -> Result, Error> { + self.has_edge(source, target).map(|_| Vec::new()) + } + + /// Return an iterator of edges out of a node, whose associated + /// label is as given. + /// + /// The efficiency of this method matters in implementations. + fn find_children_with_label( + &self, + node_id: usize, + label: &T, + ) -> Result<>::Iter<'_>, Error>; + + /// Return an iterator of labels of edges out of a node. + /// + /// The efficiency of this method matters in implementations. + fn labels_of(&self, node_id: usize) -> Result, Error>; +} + +/// A labelled graph that can be extended, but not mutated, in the +/// sense that existing nodes and edges will not be modified nor +/// removed, but new nodes can be added. The index of the new node +/// will be returned. +/// +/// Implementations can choose to keep a set of sets of edges, so that +/// new nodes will not have duplicate edge sets. In this case, the +/// returned new node index is not necessarily equal to +/// self.nodes_len() - 1, and hence the return type is designed in +/// this way. +pub trait LabelExtGraph: LabelGraph { + /// Add a new node with `edges`. + /// + /// If an edge from `edges` points to a non-existent node, return + /// an error. + fn extend(&mut self, edges: impl IntoIterator) -> Result; +} diff --git a/nfa/Cargo.toml b/nfa/Cargo.toml new file mode 100644 index 0000000..b1387b6 --- /dev/null +++ b/nfa/Cargo.toml @@ -0,0 +1,13 @@ +[package] +name = "nfa" +version = "0.1.0" +edition = "2021" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] +graph = { path = "../graph", optional = true } + +[features] +default = ["default-graph"] +default-graph = ["dep:graph"] diff --git a/nfa/src/default/mod.rs b/nfa/src/default/mod.rs new file mode 100644 index 0000000..805540b --- /dev/null +++ b/nfa/src/default/mod.rs @@ -0,0 +1,123 @@ +//! This file provides a structure that implements the trait +//! [`NFA`][super::Nfa]. +//! +//! It is used as the default implementation. + +use graph::{error::Error as GError, DLGraph, Graph, GraphLabel, LabelGraph}; + +use super::{error::Error, Nfa, Regex}; + +// TODO: Store the regular expression in the NFA as well. +// +// The current focus of the project is to understand the growth rate +// of the algorithm, to know whether I made a mistake in the previous +// iteration of the implementation, or the algorithm is not as fast as +// the author estimated, which is not quite likely, of course. +// +// Thus I shall establish a friendly interface that allows me to view +// and debug the atomic languages and the languages, transparently. + +#[non_exhaustive] +#[derive(Debug)] +/// Default NFA implementation. +pub struct DefaultNFA { + graph: DLGraph, +} + +impl Default for DefaultNFA { + fn default() -> Self { + let graph = Default::default(); + Self { graph } + } +} + +impl Graph for DefaultNFA { + type Iter<'a> = as Graph>::Iter<'a> where T: 'a; + + #[inline] + fn is_empty(&self) -> bool { + self.graph.is_empty() + } + + #[inline] + fn nodes_len(&self) -> usize { + self.graph.nodes_len() + } + + #[inline] + fn children_of(&self, node_id: usize) -> Result, GError> { + self.graph.children_of(node_id) + } + + #[inline] + fn degree(&self, node_id: usize) -> Result { + self.graph.degree(node_id) + } + + #[inline] + fn is_empty_node(&self, node_id: usize) -> Result { + self.graph.is_empty_node(node_id) + } + + #[inline] + fn has_edge(&self, source: usize, target: usize) -> Result { + self.graph.has_edge(source, target) + } +} + +impl LabelGraph for DefaultNFA { + type Iter<'a> = as LabelGraph>::Iter<'a> where T: 'a; + + type LabelIter<'a> = as LabelGraph>::LabelIter<'a> where T: 'a; + + // TODO: Return the label from the contained regular language. + #[inline] + fn vertex_label(&self, node_id: usize) -> Result, GError> { + if self.has_node(node_id) { + todo!() + } else { + Err(GError::IndexOutOfBounds(node_id, self.nodes_len())) + } + } + + #[inline] + fn edge_label(&self, source: usize, target: usize) -> Result, GError> { + self.graph.edge_label(source, target) + } + + #[inline] + fn find_children_with_label( + &self, + node_id: usize, + label: &T, + ) -> Result<>::Iter<'_>, GError> { + self.graph.find_children_with_label(node_id, label) + } + + #[inline] + fn labels_of(&self, node_id: usize) -> Result, GError> { + self.graph.labels_of(node_id) + } +} + +impl Nfa for DefaultNFA { + #[allow(unused)] + fn to_nfa(regex: impl Regex) -> Self { + todo!() + } + + fn remove_epsilon(&mut self) -> Result<(), Error> { + todo!() + } + + fn remove_dead(&mut self) -> Result<(), Error> { + todo!() + } + + fn nulling(&mut self) -> Result<(), Error> { + todo!() + } +} + +#[cfg(test)] +mod default_nfa_test {} diff --git a/nfa/src/error.rs b/nfa/src/error.rs new file mode 100644 index 0000000..6112878 --- /dev/null +++ b/nfa/src/error.rs @@ -0,0 +1,30 @@ +//! This file implements the error type for the crate. + +use graph::error::Error as GError; + +use std::fmt::{Display, Formatter}; + +#[derive(Debug, Clone, Eq, PartialEq, Ord, PartialOrd)] +pub enum Error { + UnknownNode(usize), + UnsupportedOperation, + Graph(GError), +} + +impl Display for Error { + fn fmt(&self, f: &mut Formatter<'_>) -> std::fmt::Result { + match self { + Error::UnknownNode(id) => write!(f, "unknown node: {id}"), + Error::UnsupportedOperation => write!(f, "unsupported operation"), + Error::Graph(e) => write!(f, "graph error: {e}"), + } + } +} + +impl std::error::Error for Error {} + +impl From for Error { + fn from(e: GError) -> Self { + Self::Graph(e) + } +} diff --git a/nfa/src/lib.rs b/nfa/src/lib.rs new file mode 100644 index 0000000..ef207cf --- /dev/null +++ b/nfa/src/lib.rs @@ -0,0 +1,94 @@ +#![warn(missing_docs)] +//! This crate implements non-deterministic finite automata. +//! +//! By default this uses the graph from the crate [`graph`]. To use +//! another external graph, add a module in which the external graph +//! implements the Graph trait from the [`graph`] crate, and then use +//! that external graph type as [`Graph`][graph::Graph] here. + +mod error; + +extern crate graph; + +use core::fmt::Display; + +use graph::{Graph, GraphLabel, LabelGraph}; + +use error::Error; + +/// The expected behaviour of a regular language. +/// +/// Nondeterministic finite automata are equivalent to regular +/// languages. Since regular languages are easier to understand for a +/// human being, nondeterministic finite automata include the data for +/// the equivalent regular languages. +pub trait Regex: Graph + Display { + /// Return the label of a vertex, or an error if the node is + /// invalid. + fn vertex_label(&self, node_id: usize) -> Result; + + #[inline] + /// Return the root node of the regular language. + /// + /// Implementations can follow different conventions for the root + /// node, and hence this function. + /// + /// If the regular language is empty, the implementation should + /// return None. + /// + /// The default implementation uses the convention that the root + /// node is always the first node. + fn root(&self) -> Option { + if self.is_empty() { + None + } else { + Some(0) + } + } + + // TODO: add functions that determine if certain "positions" in a + // regular language satisfy some special properties, like at the + // end of a Kleene star, or at the end of a regular language, et + // cetera. These will be needed later. +} + +/// The expected behvaiour of a nondeterministic finite automaton. +/// +/// Every NFA is a special labelled graph, so this trait extends the +/// [`LabelGraph`][graph::LabelGraph] trait. +pub trait Nfa: LabelGraph { + /// Remove all empty transitions from the nondeterministic finite + /// automaton. + fn remove_epsilon(&mut self) -> Result<(), Error>; + + /// Return a state-minimal NFA equivalent with the original one. + /// + /// This is not required. It is just to allow me to experiment + /// with NFA optimization algorithms. + fn minimize(&self) -> Result { + Err(Error::UnsupportedOperation) + } + + /// Build a nondeterministic finite automaton out of a regular + /// language. + fn to_nfa(regex: impl Regex) -> Self; + + /// Remove all dead states from the nondeterministic finite + /// automaton. + /// + /// A state is dead if there are no edges going to the state. + fn remove_dead(&mut self) -> Result<(), Error>; + + /// For each empty transition from A to B, and for every edge from + /// B to C, say, add an edge from A to C. + /// + /// This is needed specifically by the algorithm to produce a set + /// of atomic languages that represent "null-closed" derived + /// languages. + fn nulling(&mut self) -> Result<(), Error>; +} + +pub mod default; + +#[cfg(test)] +mod nfa_tests {} diff --git a/receme/Cargo.toml b/receme/Cargo.toml new file mode 100644 index 0000000..dccf28c --- /dev/null +++ b/receme/Cargo.toml @@ -0,0 +1,9 @@ +[package] +name = "receme" +version = "0.1.0" +edition = "2021" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] + diff --git a/receme/src/algebra.rs b/receme/src/algebra.rs new file mode 100644 index 0000000..49e0932 --- /dev/null +++ b/receme/src/algebra.rs @@ -0,0 +1,14 @@ +//! This file defines the algebra trait. +//! +//! If F is an endo-functor, then an F-algebra is a natural +//! transformation from F to the identity functor. + +use super::functor::Functor; + +/// An algebra is a function from F(T) to T. +/// +/// This is a "trait alias". Since Rust does not support trait alias +/// yet, we define an empty trait with an automatic implementation. +pub trait Algebra>: FnMut(F) -> T {} + +impl, A: FnMut(F) -> T> Algebra for A {} diff --git a/receme/src/catana.rs b/receme/src/catana.rs new file mode 100644 index 0000000..e3d4728 --- /dev/null +++ b/receme/src/catana.rs @@ -0,0 +1,27 @@ +//! This file defines behaviours of catamorphisms and anamorphisms. +//! +//! A catamorphism collapses a recursive structure into a flat value, +//! whereas an anamorphism expands a value into a recursive structure. + +use crate::{algebra::Algebra, coalgebra::Coalgebra, functor::Functor}; + +/// A type that implements Cata is capable of being collapsed into a single value. +/// +/// The catamorphism consumes `self`. +pub trait Cata, A: Algebra> { + /// A catamorphism takes a recursive structure and an algebra for + /// the recursive structure, and returns a single, flat, collapsed + /// value. + fn cata(self, alg: A) -> T; +} + +/// A type that implements Ana is capable of being expanded from a +/// flat value. +/// +/// The anamorphism consumes `self`. +pub trait Ana, C: Coalgebra> { + /// An anamorphism takes a single, flat, collapsed value and a + /// co-algebra for a recursive structure, and returns that + /// recursive structure. + fn ana(value: T, coalg: C) -> Self; +} diff --git a/receme/src/coalgebra.rs b/receme/src/coalgebra.rs new file mode 100644 index 0000000..5974d90 --- /dev/null +++ b/receme/src/coalgebra.rs @@ -0,0 +1,14 @@ +//! This file defines the co-algebra trait. +//! +//! If F is an endo-functor, then an F-co-algebra is a natural +//! transformation from the identity functor to F. + +use super::functor::Functor; + +/// A co-algebra is a function from T to F(T). +/// +/// This is a "trait alias". Since Rust does not support trait alias +/// yet, we define an empty trait with an automatic implementation. +pub trait Coalgebra>: FnMut(T) -> F {} + +impl, C: FnMut(T) -> F> Coalgebra for C {} diff --git a/receme/src/coralgebra.rs b/receme/src/coralgebra.rs new file mode 100644 index 0000000..a4a73d2 --- /dev/null +++ b/receme/src/coralgebra.rs @@ -0,0 +1,28 @@ +//! This file defines the behaviours of R-co-algebras. +//! +//! For a functor F, an R-co-algebra is a natural transformation from +//! the identity functor to F1, where F1 is the functor that sends T +//! to F(F(T) + T), where the + is the categorical co-product, +//! represented in Rust as `Result`. And the F(T) variant means to +//! short-circuit the expansion. + +use crate::functor::Functor; + +/// An R-co-algebra is a function from T to F(Result). +/// +/// This is a "trait alias". Since Rust does not support trait alias +/// yet, we define an empty trait with an automatic implementation. +pub trait Coralgebra: FnMut(T) -> G +where + F: Functor, + G: Functor>, +{ +} + +impl Coralgebra for R +where + F: Functor, + G: Functor>, + R: FnMut(T) -> G, +{ +} diff --git a/receme/src/functor.rs b/receme/src/functor.rs new file mode 100644 index 0000000..95e2555 --- /dev/null +++ b/receme/src/functor.rs @@ -0,0 +1,64 @@ +//! This file defines the Functor trait. +//! +//! This is the basis of the recursion scheme. +//! +//! More precisely, this file provides two versions of functor traits: +//! one whose `map` function consumes `self`, and one whose `map` does +//! not. + +/// A functor can map over its generic parameter. +/// +/// It can map from Functor(T) to Functor(S). +pub trait Functor { + /// The target of the map. + /// + /// Since Rust has no higher-kinded polymorphism, we have to + /// express this type explicitly. + /// + /// # Note + /// + /// This is a generic associated type, so we need a minimal Rust + /// version of 1.65, when this feature was first introduced to + /// stable Rust. + type Target: Functor; + + /// Map from Functor(T) to Functor(S). + /// + /// # Note + /// + /// This consumes `self`. If one wants not to consume `self`, + /// then consider the trait [`FunctorRef`]. + fn fmap(self, f: impl FnMut(T) -> S) -> Self::Target; +} + +/// A functor can map over its generic type parameter. +/// +/// It can map from Functor(T) to Functor(S). +/// +/// This is similar to [`Functor`], but the +/// [`fmap`][FunctorRef::fmap_ref] method takes a reference and +/// does not consume `self`. +pub trait FunctorRef { + /// The target of the map. + /// + /// Since Rust has no higher-kinded polymorphism, we have to + /// express this type explicitly. + /// + /// # Note + /// + /// This is a generic associated type, so we need a minimal Rust + /// version of 1.65, when this feature was first introduced to + /// stable Rust. + type Target: Functor; + + /// Map from Functor(T) to Functor(S). + /// + /// # Note + /// + /// This does notconsume `self`. If one wants to consume `self`, + /// then consider the trait [`Functor`]. + /// + /// To avoid having to specify the trait when calling the method, + /// we give it a distinct name. + fn fmap_ref(&self, f: impl FnMut(T) -> S) -> Self::Target; +} diff --git a/receme/src/hylo.rs b/receme/src/hylo.rs new file mode 100644 index 0000000..8d26c19 --- /dev/null +++ b/receme/src/hylo.rs @@ -0,0 +1,41 @@ +//! This file defines the behaviour of hylomorphisms. +//! +//! A hylomorphism is a composition of an anamorphism with a +//! catamorphism. But it is separated into a distinct trait as we can +//! implement hylomorphisms more efficiently by short-circuiting +//! during the expansion by the anamorphism. + +use crate::{ + algebra::Algebra, + catana::{Ana, Cata}, + coalgebra::Coalgebra, + functor::Functor, +}; + +/// A type implementing Hylo is able to expand from a value of type +/// `U` into a recursive structure holding values of type `G`, and +/// also to collapse from that recursive structure to a value of type +/// `T`. +/// +/// Types which implement [`Cata`] and [`Ana`] compatibly can +/// automatically implement [`Hylo`] as follows. +/// +/// But of course this is not efficient, and types should implement in +/// a more efficient manner, if available. +/// +/// ```ignore +/// Inter::ana(value, coalg).cata(alg) +/// ``` +pub trait Hylo: Cata + Ana +where + F: Functor, + G: Functor = F>, + H: Functor = G>, + A: Algebra, + C: Coalgebra, +{ + /// Expand from `value` to an intermediate recursive structure, by + /// means of a coalgebra, and then collapse into the result value, + /// by means of an algebra. + fn hylo(value: U, alg: A, coalg: C) -> T; +} diff --git a/receme/src/lib.rs b/receme/src/lib.rs new file mode 100644 index 0000000..be1f028 --- /dev/null +++ b/receme/src/lib.rs @@ -0,0 +1,227 @@ +#![warn(missing_docs)] +//! This crate implements some recursion schemes in Rust. +//! +//! The name "receme" is a mix of "Recursion Scheme". +//! +//! See [this series of five blog +//! articles](https://blog.sumtypeofway.com/posts/introduction-to-recursion-schemes.html) +//! for an introduction to recursion schemes, and see [this series of +//! three articles](https://recursion.wtf/posts/rust_schemes/) for +//! where I got inspired to write this library. +//! +//! Note that, since Rust does not have higher-kinded polymorphism, it +//! is sometimes cumbersome to implement some notions, though. +//! +//! # Another crate +//! +//! The author of the above-mentionned three-article series has +//! already implemented the recursion schemes in Rust, in [this +//! repository](https://github.com/inanna-malick/recursion), so why do +//! it myself? +//! +//! One reason is that I want my package to not depend on anything +//! other than the default Rust toolchains. This is perhaps not a +//! very convincing reason, but I just want to do so. +//! +//! Another reason is that I want the design to be modular: if there +//! is another crate that provides a similar functionality, I can +//! quickly switch the underlying mechanism to adopt to the new crate +//! instead. +//! +//! Consequently I decided to write this library, and provide a +//! default implementation. This way by default the package does not +//! depend on external crates, and if so demanded, can switch to use +//! an external crate instantaneously, at least hopefully. + +// The following modules are for traits. +pub mod algebra; +pub mod catana; +pub mod coalgebra; +pub mod coralgebra; +pub mod functor; +pub mod hylo; +pub mod parapo; +pub mod ralgebra; + +// pub mod futhis; + +// The following modules are for default implementations. +pub mod tree; + +// TODO: benchmarks + +#[cfg(test)] +mod test_expr_tree { + use super::{ + catana::{Ana, Cata}, + functor::Functor, + hylo::Hylo, + tree::{DFTree, TEStrategy, Tree, TreeIndex}, + }; + + // Just for testing const generics and fixed size arrays, that is + // to say, just for fun. + + // fn demo(v: Vec) -> Result<[T; N], String> { + // v.try_into() + // .map_err(|v: Vec| format!("expected a vector of length {N}, but got {}", v.len())) + // } + + // #[test] + // fn test_demo() -> Result<(), String> { + // let v: Vec = vec![1, 2, 3]; + // let w: Vec = vec![1, 2]; + + // assert_eq!(demo::<_, 2>(w)?, [1, 2]); + // assert_eq!(demo::<_, 3>(v)?, [1, 2, 3]); + + // Ok(()) + // } + + #[derive(Debug, Clone)] + enum Expr { + Add(T, T), + Lit(isize), + } + + impl Functor for Expr { + type Target = Expr; + + fn fmap(self, mut f: impl FnMut(T) -> S) -> Self::Target { + match self { + Expr::Add(a, b) => Expr::Add(f(a), f(b)), + Expr::Lit(value) => Expr::Lit(value), + } + } + } + + #[test] + fn test_cata() { + /// This is an Expr-algebra, but only for a specific type, + /// `isize`. + fn eval(expr: Expr) -> isize { + match expr { + Expr::Add(a, b) => a + b, + Expr::Lit(value) => value, + } + } + + /// Use a temporary function to construct a tree. + /// + /// Should use an anamorphism for this purpose, later. + fn construct_tree() -> Tree> { + use Expr::{Add, Lit}; + + let strategy: TEStrategy = TEStrategy::UnsafeArena; + + // This represents the following expression + // + // Add(1, Add(3, Add(10, -1))). + let elements = vec![ + Add(1, 2).fmap(TreeIndex::new), + Lit(1), + Add(3, 4).fmap(TreeIndex::new), + Lit(3), + Add(5, 6).fmap(TreeIndex::new), + Lit(10), + Lit(-1), + ]; + + Tree::new(elements, strategy) + } + + let tree = construct_tree(); + + let result = tree.cata(eval); + + assert_eq!(result, 13isize); + } + + #[test] + fn test_ana() { + // Just a ugly hack, haha. + let mut vector: Vec> = vec![ + Expr::Add(1, 2).fmap(TreeIndex::new), + Expr::Lit(1), + Expr::Add(3, 4).fmap(TreeIndex::new), + Expr::Lit(3), + Expr::Add(5, 6).fmap(TreeIndex::new), + Expr::Lit(10), + Expr::Lit(-14), + ]; + + let mut vector1: Vec> = vec![ + Expr::Add(1, 2).fmap(TreeIndex::new), + Expr::Lit(1), + Expr::Add(3, 4).fmap(TreeIndex::new), + Expr::Lit(3), + Expr::Add(5, 6).fmap(TreeIndex::new), + Expr::Lit(10), + Expr::Lit(-14), + ]; + + let mut tree = Tree::ana(TreeIndex::new(0), |value: TreeIndex| { + // This is safe since we visit each valid node exactly + // once. + std::mem::replace(&mut vector[*value], Expr::Lit(0)) + }); + + tree.set_strategy(TEStrategy::UnsafeArena); + + let tree = tree; + + println!("tree is {tree:#?}"); + + let result = tree.cata(|expr| match expr { + Expr::Add(a, b) => a + b, + Expr::Lit(v) => v, + }); + + assert_eq!(result, 0); + + // test df_tree + let dftree = DFTree::ana(TreeIndex::new(0), |value: TreeIndex| { + // This is safe since we visit each valid node exactly + // once. + std::mem::replace(&mut vector1[*value], Expr::Lit(0)) + }); + + let tree = dftree.to_tree(); + + println!("dftree = {tree:#?}"); + + let result = tree.cata(|expr| match expr { + Expr::Add(a, b) => a + b, + Expr::Lit(v) => v, + }); + + assert_eq!(result, 0); + } + + #[test] + fn test_hylo() { + // Again using the ugly hack + let vector: Vec> = vec![ + Expr::Add(1, 2).fmap(TreeIndex::new), + Expr::Lit(1), + Expr::Add(3, 4).fmap(TreeIndex::new), + Expr::Lit(3), + Expr::Add(5, 6).fmap(TreeIndex::new), + Expr::Lit(10), + Expr::Lit(14), + ]; + + fn eval_expr(mut v: Vec>) -> isize { + Tree::hylo( + TreeIndex::new(0), + |expr| match expr { + Expr::Add(a, b) => a + b, + Expr::Lit(v) => v, + }, + |value: TreeIndex| std::mem::replace(&mut v[*value], Expr::Lit(0)), + ) + } + + assert_eq!(eval_expr(vector), 28); + } +} diff --git a/receme/src/parapo.rs b/receme/src/parapo.rs new file mode 100644 index 0000000..11cc613 --- /dev/null +++ b/receme/src/parapo.rs @@ -0,0 +1,44 @@ +//! This file defines behaviours of paramorphisms and apomorphisms. +//! +//! A paramorphism is a generalization of a catamorphism. Instead of +//! using an algebra, which is a function from F(T) to T, we use an +//! R-algebra, which is a function from F(T, F(T)) to T. The extra +//! F(T) represents the contexts where the collapsing happens. +//! +//! An apomorphism is a generalization of anamorphism. It is the +//! categorical dual of a paramorphism. So it uses an R-co-algebra, +//! which is a function from T to F(F(T) + T), where the latter sum is +//! the categorical co-product. + +use crate::{coralgebra::Coralgebra, functor::Functor, ralgebra::RAlgebra}; + +/// A type that implements Para is capable of being collapsed to a +/// single value by use of an R-Algebra. +/// +/// The paramorphism consumes `self`. +pub trait Para +where + F: Functor, + R: RAlgebra, +{ + /// A paramorphism takes a recursive structure and an R-algebra + /// for that recursive structure, and returns a single, flat, + /// collapsed value. + fn para(self, ralg: R) -> T; +} + +/// A type that implements Apo is capable of being expanded from a +/// flat value by use of an R-co-algebra. +/// +/// The apomorphism consumes `self`. +pub trait Apo +where + F: Functor, + G: Functor>, + C: Coralgebra, +{ + /// An apomorphism takes single, flat, collapsed value and an + /// R-co-algebra for a recursive structure, and returns that + /// recursive structure. + fn apo(value: T, rcoalg: C) -> Self; +} diff --git a/receme/src/ralgebra.rs b/receme/src/ralgebra.rs new file mode 100644 index 0000000..989089e --- /dev/null +++ b/receme/src/ralgebra.rs @@ -0,0 +1,25 @@ +//! This file defines the behaviours of R-algebras. +//! +//! For a functor F, an R-algebra is a natural transformation from F1 +//! to the identity functor, where F1 is the functor that sends T to +//! F((F(T), T)). This extra F(T) represents the context during the +//! computations. + +use crate::functor::Functor; + +/// An R-algebra is a function from F((F(T), T)) to T. +/// +/// This is a "trait alias". Since Rust does not support trait alias +/// yet, we define an empty trait with an automatic implementation. +pub trait RAlgebra: FnMut((T, F)) -> T +where + F: Functor, +{ +} + +impl RAlgebra for R +where + F: Functor, + R: FnMut((T, F)) -> T, +{ +} diff --git a/receme/src/tree.rs b/receme/src/tree.rs new file mode 100644 index 0000000..eb64f31 --- /dev/null +++ b/receme/src/tree.rs @@ -0,0 +1,368 @@ +//! This file implements a recursive structure that implements the +//! recursion scheme traits, representing trees. +//! +//! The tree is backed by a vector. + +use crate::{ + algebra::Algebra, + catana::{Ana, Cata}, + coalgebra::Coalgebra, + functor::Functor, + hylo::Hylo, +}; + +use std::{collections::VecDeque, mem::MaybeUninit, ops::Deref}; + +/// The evaluation strategy for the tree. +#[derive(Default, Debug, Copy, Clone)] +pub enum TEStrategy { + #[default] + /// This strategy uses an arena, and uses an `Option` to store + /// the data. + /// + /// # Comparison: + /// + /// Since it is an arena, it saves allocations, compared to the + /// variant [`DepthFirst`][TEStrategy::DepthFirst]. But it needs + /// indices to operate, so uses more memory. + /// + /// On the other hand, it uses an option, so is slower than the + /// variant [`UnsafeArena`][TEStrategy::UnsafeArena], but avoids + /// unsafe code altogether. Applications can first use this + /// variant to make sure the algorithm works, before converting to + /// use the unsafe variant. + SafeArena, + /// This strategy uses an arena, and uses an `MaybeUninit` to + /// store the data. + /// + /// # Comparison: + /// + /// Since it is an arena, it saves allocations, compared to the + /// variant [`DepthFirst`][TEStrategy::DepthFirst]. But it needs + /// indices to operate, so uses more memory. + /// + /// On the other hand, it uses a `MaybeUninit`, so is faster than + /// the variant [`SafeArena`][TEStrategy::SafeArena], but uses + /// unsafe code. Applications can first use the safe variant to + /// make sure the algorithm works, before converting to use this + /// variant. + UnsafeArena, + /// This strategy uses a plain vector. + /// + /// # Comparison: + /// + /// Since it is a plain vector, it uses more allocations, compared + /// to other variants. But it does not use indices, so consumes + /// less memory. + /// + /// # Warning + /// + /// Since it uses no indices, it relies on the depth-first order + /// of the elements to correctly find elements. This puts a + /// requirement on the implementation of the [`Functor`] trait. + DepthFirst, +} + +/// A tree is just a wrapper around a vector. +/// +/// # Warning +/// +/// The tree is supposed to be stored in topological order. This +/// order is used in a critical way in the implementations of +/// recursion schemes. Violations of this assumption are fatal to +/// using those trait methods. +#[derive(Clone, Debug)] +pub struct Tree { + elements: Vec, + strategy: TEStrategy, +} + +impl Tree { + #[inline] + /// Construct a new tree. + pub fn new(elements: Vec, strategy: TEStrategy) -> Self { + Self { elements, strategy } + } + + /// Just a function for testing. + /// + /// # Warning + /// + /// This is definitely going to be removed in the future. + pub fn nth(&self, n: usize) -> Option<&T> { + self.elements.get(n) + } + + #[inline] + /// Retrieve the strategy of the tree. + pub fn strategy(&self) -> TEStrategy { + self.strategy + } + + #[inline] + /// Set the strategy of the tree. + pub fn set_strategy(&mut self, strategy: TEStrategy) { + self.strategy = strategy; + } +} + +// Manual implementation can avoid unnecessary requirement on the +// parameter `T`. +impl Default for Tree { + fn default() -> Self { + let elements = Vec::new(); + let strategy = TEStrategy::default(); + + Self { elements, strategy } + } +} + +#[derive(Debug, Copy, Clone)] +/// A thin wrapper around `usize`, to index vectors. +/// +/// By means of the [*newtype +/// pattern*](https://doc.rust-lang.org/rust-by-example/generics/new_types.html) +/// in Rust, it is supposed to be treated as a simple `usize` in the +/// compiled codes. +pub struct TreeIndex(usize); + +impl TreeIndex { + /// Wrap an index in this type. + pub fn new(index: usize) -> Self { + Self(index) + } +} + +impl Deref for TreeIndex { + type Target = usize; + + fn deref(&self) -> &Self::Target { + &self.0 + } +} + +impl Cata for Tree +where + F: Functor, + G: Functor = F>, + A: Algebra, +{ + fn cata(self, mut alg: A) -> T { + // First deal with the safe case + match self.strategy { + TEStrategy::SafeArena => { + let mut results: Vec> = std::iter::repeat_with(Default::default) + .take(self.elements.len()) + .collect(); + + for (index, node) in self.elements.into_iter().enumerate().rev() { + let algebra_result = { + let node = node.fmap::(|index| { + std::mem::replace(&mut results[*index], None).unwrap() + }); + + alg(node) + }; + + // Artificially use this value to satisfy the compiler. + let _ = std::mem::replace(&mut results[index], Some(algebra_result)); + } + + std::mem::replace(&mut results[0], None).unwrap() + } + TEStrategy::UnsafeArena => { + let mut results: Vec> = std::iter::repeat_with(MaybeUninit::uninit) + .take(self.elements.len()) + .collect(); + + for (index, node) in self.elements.into_iter().enumerate().rev() { + let algebra_result = { + let node = node.fmap::(|index| unsafe { + std::mem::replace(&mut results[*index], MaybeUninit::uninit()) + .assume_init() + }); + + alg(node) + }; + + results[index].write(algebra_result); + } + + unsafe { std::mem::replace(&mut results[0], MaybeUninit::uninit()).assume_init() } + } + TEStrategy::DepthFirst => { + let mut results_stack: Vec = Vec::new(); + + for node in self.elements.into_iter().rev() { + // Replace each node data with the value from the + // results stack. + let mapped_node = node.fmap(|_| results_stack.pop().unwrap()); + + results_stack.push(alg(mapped_node)); + } + + results_stack.pop().unwrap() + } + } + } +} + +impl Ana for Tree +where + F: Functor = G>, + G: Functor, + C: Coalgebra, +{ + /// An anamorphism takes a single, flat, collapsed value and a + /// co-algebra for a recursive structure, and returns that + /// recursive structure. + /// + /// # Descriptions + /// + /// This always generates a tree which uses the default strategy. + /// If one wants to use a different strategy, set the strategy + /// after generating the tree. + /// + /// # See also + /// + /// To use the depth first strategy to generate the tree, use the + /// wrapper struct [`DFTree`]. + fn ana(value: T, mut coalg: C) -> Self { + let mut queue = VecDeque::new(); + + queue.push_back(value); + + let mut elements = vec![]; + + let strategy = TEStrategy::default(); + + while let Some(value) = queue.pop_back() { + let expanded_layer = coalg(value); + + let mapped_layer = expanded_layer.fmap::(|value| { + queue.push_back(value); + + TreeIndex(elements.len() + queue.len()) + }); + + elements.push(mapped_layer); + } + + Self { elements, strategy } + } +} + +/// To generate a tree with the strategy +/// [`DepthFirst`][TEStrategy::DepthFirst], we use a wrapper struct +/// which implements [`Ana`] in the desired manner. +#[derive(Debug, Clone)] +pub struct DFTree(Tree); + +impl DFTree { + #[inline] + /// Convert to the underlying tree. + pub fn to_tree(self) -> Tree { + self.0 + } + + #[inline] + /// Wrap a tree. + pub fn new(tree: Tree) -> Self { + Self(tree) + } +} + +impl Ana for DFTree +where + F: Functor = G>, + G: Functor, + C: Coalgebra, +{ + /// An anamorphism takes a single, flat, collapsed value and a + /// co-algebra for a recursive structure, and returns that + /// recursive structure. + /// + /// # Descriptions + /// + /// This always generates a tree which uses the depth first + /// strategy. If one wants to use a different strategy, set the + /// strategy after generating the tree. + /// + /// # See also + /// + /// To use the default strategy to generate the tree, use the + /// original struct [`Tree`]. + fn ana(value: T, mut coalg: C) -> Self { + let mut stack = Vec::new(); + + stack.push(value); + + let mut elements = vec![]; + + let strategy = TEStrategy::DepthFirst; + + while let Some(value) = stack.pop() { + let expanded_layer = coalg(value); + + let mut local_stack = Vec::new(); + + let mapped_layer = expanded_layer.fmap::(|value| { + local_stack.push(value); + + // The index is of no meaning here, since we rely on + // the depth-first order. + TreeIndex(0) + }); + + stack.extend(local_stack.into_iter().rev()); + + elements.push(mapped_layer); + } + + Self::new(Tree::new(elements, strategy)) + } +} + +impl Hylo for Tree +where + F: Functor, + G: Functor = F>, + H: Functor = G>, + A: Algebra, + C: Coalgebra, +{ + fn hylo(value: U, mut alg: A, mut coalg: C) -> T { + // The hylomorphism ignores the tree. Maybe I will add + // different implementations later on. + + let mut result_stack: Vec = Vec::new(); + let mut value_node_stack: Vec> = vec![Ok(value)]; + + while let Some(value_or_node) = value_node_stack.pop() { + match value_or_node { + Ok(value) => { + let node = coalg(value); + + let mut local_values: Vec = Vec::new(); + + let mapped_node = node.fmap(|node_value| { + local_values.push(node_value); + TreeIndex::new(0) + }); + + value_node_stack.push(Err(mapped_node)); + value_node_stack.extend(local_values.into_iter().rev().map(Ok)); + } + Err(node) => { + let mapped_node = node.fmap(|_| result_stack.pop().unwrap()); + + result_stack.push(alg(mapped_node)); + } + } + } + + result_stack.pop().unwrap() + } +} + +// TODO: Para, Apo, Histo, and Futu await us. diff --git a/repcore/Cargo.toml b/repcore/Cargo.toml new file mode 100644 index 0000000..7416ad5 --- /dev/null +++ b/repcore/Cargo.toml @@ -0,0 +1,8 @@ +[package] +name = "repcore" +version = "0.1.0" +edition = "2021" + +# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html + +[dependencies] diff --git a/repcore/src/lib.rs b/repcore/src/lib.rs new file mode 100644 index 0000000..7d12d9a --- /dev/null +++ b/repcore/src/lib.rs @@ -0,0 +1,14 @@ +pub fn add(left: usize, right: usize) -> usize { + left + right +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn it_works() { + let result = add(2, 2); + assert_eq!(result, 4); + } +} diff --git a/src/lib.rs b/src/lib.rs new file mode 100644 index 0000000..7d12d9a --- /dev/null +++ b/src/lib.rs @@ -0,0 +1,14 @@ +pub fn add(left: usize, right: usize) -> usize { + left + right +} + +#[cfg(test)] +mod tests { + use super::*; + + #[test] + fn it_works() { + let result = add(2, 2); + assert_eq!(result, 4); + } +} -- cgit v1.2.3-18-g5258