From 55f7068e91182dfe458fad41c3251388ea461569 Mon Sep 17 00:00:00 2001
From: JSDurand <mmemmew@gmail.com>
Date: Thu, 10 Aug 2023 11:15:53 +0800
Subject: Add an example 'bfinterp'

My plan is to build a little interpreter for an esoteric programming
language as the most basic application of this package, before
embarking on some more ambitious applications.
---
 examples/bfinterp.rs     | 84 ++++++++++++++++++++++++++++++++++++++++++++++++
 test-data/brainfuck.abnf |  4 +++
 2 files changed, 88 insertions(+)
 create mode 100644 examples/bfinterp.rs
 create mode 100644 test-data/brainfuck.abnf

diff --git a/examples/bfinterp.rs b/examples/bfinterp.rs
new file mode 100644
index 0000000..d5a0c2a
--- /dev/null
+++ b/examples/bfinterp.rs
@@ -0,0 +1,84 @@
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let input_str = if let Some(string) = std::env::args().skip(1).next() {
+        string
+    } else {
+        return Err("An input program is required.".into());
+    };
+
+    let input = tokenize(&input_str)?;
+
+    let grammar_string = "brainfuck = *unit
+
+unit = \">\" / \"<\" / \"+\" / \"-\" / \",\" / \";\" /
+       \"[\" brainfuck \"]\"";
+
+    let grammar: grammar::Grammar = grammar_string.parse().map_err(|err| format!("{err}"))?;
+
+    println!("grammar = {grammar}");
+
+    let atom: chain::atom::DefaultAtom =
+        chain::atom::DefaultAtom::from_grammar(grammar).map_err(|err| format!("{err}"))?;
+
+    // atom.print_viz("nfa.gv")?;
+
+    use chain::Chain;
+
+    let mut chain: chain::default::DefaultChain =
+        chain::default::DefaultChain::unit(atom).map_err(|err| format!("{err}"))?;
+
+    // let input = [0, 1, 6, 2, 6, 3, 4, 6, 5, 2, 7, 4, 7, 3, 2, 7, 2];
+
+    for (index, token) in input.iter().copied().enumerate() {
+        chain.chain(token, index, false)?;
+        // if (5..=12).contains(&index) {
+        //     chain.print_current(&format!("chain {index}.gv"))?;
+        // }
+    }
+
+    let _extracted = chain.end_of_input(input.len(), input[input.len() - 1])?;
+
+    // use graph::Graph;
+
+    // extracted.print_viz("bf.gv")?;
+
+    Ok(())
+}
+
+fn tokenize(input: &str) -> Result<Vec<usize>, String> {
+    let mut result: Vec<usize> = Vec::with_capacity(input.len());
+
+    for (index, c) in input.chars().enumerate() {
+        match c {
+            '>' => {
+                result.push(0);
+            }
+            '<' => {
+                result.push(1);
+            }
+            '+' => {
+                result.push(2);
+            }
+            '-' => {
+                result.push(3);
+            }
+            ',' => {
+                result.push(4);
+            }
+            ';' => {
+                result.push(5);
+            }
+            '[' => {
+                result.push(6);
+            }
+            ']' => {
+                result.push(7);
+            }
+            ' ' | '\t' | '\n' | '\r' => {}
+            _ => {
+                return Err(format!("Unknown character {c} at {index}"));
+            }
+        }
+    }
+
+    Ok(result)
+}
diff --git a/test-data/brainfuck.abnf b/test-data/brainfuck.abnf
new file mode 100644
index 0000000..df3d1da
--- /dev/null
+++ b/test-data/brainfuck.abnf
@@ -0,0 +1,4 @@
+brainfuck = *unit
+
+unit  = ">" / "<" / "+" / "-" / "," / ";" /
+        "[" brainfuck "]"
-- 
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