start work on lexer

.gitignore

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+target/
+.vscode/

Cargo.lock

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+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "regex-engine"
+version = "0.1.0"

Cargo.toml

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+[package]
+name = "regex-engine"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]

src/lexer.rs

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+use std::iter::Peekable;
+
+#[derive(Debug)]
+pub enum Token {
+    Character(char),
+    CharacterRange(char, char)
+}
+
+#[derive(Debug)]
+pub struct Lexer<I> 
+where
+    I: Iterator<Item = char>
+{
+    scanner: Peekable<I>
+}
+
+impl<I> Lexer<I>
+where
+    I: Iterator<Item = char> 
+{
+    pub fn new(scanner: I) -> Lexer<I> {
+        Lexer {
+            scanner: scanner.peekable()
+        }
+    }
+
+    fn handle_character(&mut self) -> Option<Token> {
+        let character = self.scanner.next()?;
+
+        if let Some(dash) = self.scanner.peek() {
+            if *dash == '-' {
+                return Some(Token::CharacterRange(character, self.scanner.nth(1)?));
+            }
+        }
+
+        Some(Token::Character(character))
+    }
+}
+
+impl<I> Iterator for Lexer<I>
+where 
+    I: Iterator<Item = char> 
+{
+    type Item = Token;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let symbol = self.scanner.peek()?;
+
+        match symbol {
+            '-' => todo!(),
+            '^' => todo!(),
+            '$' => todo!(),
+            '\\' => todo!(),
+            '.' => todo!(),
+            '*' => todo!(),
+            '+' => todo!(),
+            '?' => todo!(),
+            '(' => todo!(),
+            ')' => todo!(),
+            '[' => todo!(),
+            ']' => todo!(),
+            '{' => todo!(),
+            '}' => todo!(),
+            '|' => todo!(),
+
+            _ => self.handle_character()
+        }
+    }
+}

src/main.rs

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+mod parser;
+mod lexer;
+
+fn main() {
+    let output = match parser::parse_string("Hello A-Ztesting!") {
+        Ok(val) => val,
+        Err(e) => panic!("{e}")
+    };
+
+
+}

src/parser.rs

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+use std::iter::Peekable;
+
+use crate::lexer::Lexer;
+
+#[derive(Debug)]
+pub struct Parser<I>
+where 
+    I: Iterator<Item = char> 
+{
+    lexer: Peekable<Lexer<I>>
+} 
+
+impl<I> Parser<I>
+where
+    I: Iterator<Item = char>
+{
+    fn new(scanner: I) -> Parser<I> {
+        Parser {
+            lexer: Lexer::new(scanner).peekable()
+        }
+    }
+
+    fn parse(self) -> Result<(), String> {
+        self.lexer.for_each(|token| println!("{token:?}",));
+        Ok(())
+    }
+}
+
+pub fn parse_string(input: &str) -> Result<(), String> {
+    let scanner = input.chars();
+
+    Parser::new(scanner).parse()?;
+
+    Ok(())
+}