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|
//! This file implements a type of labels that could be used as the
//! labels of a parse forest.
use super::*;
/// The actual label of a grammar label.
#[derive(Debug, Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
pub enum GrammarLabelType {
/// A terminal or a non-terminal.
TNT(TNT),
/// A rule position.
Rule(usize),
}
impl Display for GrammarLabelType {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
match self {
Self::TNT(tnt) => write!(f, "{tnt}"),
Self::Rule(pos) => write!(f, "R({pos})"),
}
}
}
// Some convenient conversions
impl From<usize> for GrammarLabelType {
#[inline]
fn from(r: usize) -> Self {
Self::Rule(r)
}
}
impl From<TNT> for GrammarLabelType {
#[inline]
fn from(tnt: TNT) -> Self {
Self::TNT(tnt)
}
}
impl GrammarLabelType {
/// Return the name of this label with the help of the associated
/// grammar.
#[inline]
pub fn name(&self, grammar: &Grammar) -> Result<String, Error> {
match self {
Self::TNT(tnt) => grammar.name_of_tnt(*tnt),
Self::Rule(pos) => grammar.rule_pos_to_string(*pos),
}
}
/// Return the contained TNT, if any.
#[inline]
pub fn tnt(&self) -> Option<TNT> {
match self {
Self::TNT(tnt) => Some(*tnt),
Self::Rule(_) => None,
}
}
/// Return the contained rule position, if any.
#[inline]
pub fn rule(&self) -> Option<usize> {
match self {
Self::TNT(_) => None,
Self::Rule(pos) => Some(*pos),
}
}
}
/// The label to be used in a forest.
#[derive(Debug, Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Hash)]
pub struct GrammarLabel {
/// The actual label.
label: GrammarLabelType,
/// The start in the input that this label correponds to.
start: usize,
/// The end in the input that this label correponds to.
end: Option<usize>,
}
impl core::fmt::Display for GrammarLabel {
fn fmt(&self, f: &mut core::fmt::Formatter<'_>) -> core::fmt::Result {
write!(
f,
"{}, {}, {}",
self.label,
self.start,
if let Some(end) = self.end {
format!("{end}")
} else {
"ε".to_owned()
}
)
}
}
impl GrammarLabel {
/// Construct a new label.
#[inline]
pub fn new(label: impl Into<GrammarLabelType>, start: usize) -> Self {
let label = label.into();
let end = None;
Self { label, start, end }
}
/// Construct a new label with an ending position.
#[inline]
pub fn new_closed(label: impl Into<GrammarLabelType>, start: usize, end: usize) -> Self {
let label = label.into();
let end = Some(end);
Self { label, start, end }
}
/// Return the end in the input.
#[inline]
pub fn end(&self) -> Option<usize> {
self.end
}
/// Set the start.
#[inline]
pub fn set_start(&mut self, pos: usize) {
self.start = pos;
}
/// Return the start in the input.
#[inline]
pub fn start(&self) -> usize {
self.start
}
/// Return the actual label.
#[inline]
pub fn label(&self) -> GrammarLabelType {
self.label
}
/// Update the end.
#[inline]
pub fn set_end(&mut self, end: usize) {
self.end = Some(end);
}
/// Remove the ending boundary.
#[inline]
pub fn open_end(&mut self) {
self.end = None;
}
/// Return a string description with the help of the associated
/// grammar.
pub fn to_string(&self, grammar: &Grammar) -> Result<String, Error> {
// First calculate the length of the resulting string.
let mut num = 16 + 6;
num += self.label().name(grammar)?.len();
num += format!("{} ", self.start()).len();
if let Some(end) = self.end() {
num += format!("to {end}").len();
} else {
num += 7;
}
let num = num;
let mut s = String::with_capacity(num);
s.push_str("a node labelled ");
s.push_str(&self.label().name(grammar)?);
s.push_str(" from ");
s.push_str(&format!("{} ", self.start()));
if let Some(end) = self.end() {
s.push_str(&format!("to {end}"));
} else {
s.push_str("onwards");
}
Ok(s)
}
}
|
