generic-lexer

A generic lexer in Rust using a simple match function or closure

```rust use generic_lexer::{Lexer, LexerInput, MatchError};

[derive(Debug)]

enum TokenKind { Int, Float, Name, Plus, Minus, Star, Slash, Semicolon, Equals, }

fn lexint(input: &mut LexerInput) -> TokenKind { input.nextwhile(char::isasciidigit); if input.test('.') { return lex_float(input); } TokenKind::Int }

fn lexfloat(input: &mut LexerInput) -> TokenKind { input.nextwhile(char::isasciidigit); TokenKind::Float }

fn lexname(input: &mut LexerInput) -> TokenKind { input.nextwhile(|&c| c == '' || c.isascii_alphabetic()); TokenKind::Name }

fn lex(firstchar: char, input: &mut LexerInput) -> Result { let kind = match firstchar { '+' => TokenKind::Plus, '-' => TokenKind::Minus, '*' => TokenKind::Star, '/' => TokenKind::Slash, ';' => TokenKind::Semicolon, '=' => TokenKind::Equals,

    c if c.is_ascii_digit() => lex_int(input),
    c if c.is_ascii_alphabetic() => lex_name(input),

    c => return Err(MatchError::Custom(format!("Unexpected '{}'", c)))
};

Ok(kind)

}

fn main() -> Result<(), Box> { let input = "a = 420 + 69 * 3.14;"; let lexer = Lexer::new(&input, &lex, true); let tokens = lexer.collect::, _>>()?; println!("{:#?}", tokens); Ok(()) } ```

[ Token { kind: Name, text: "a", }, Token { kind: Equals, text: "=", }, Token { kind: Int, text: "420", }, Token { kind: Plus, text: "+", }, Token { kind: Int, text: "69", }, Token { kind: Star, text: "*", }, Token { kind: Float, text: "3.14", }, Token { kind: Semicolon, text: ";", }, ]