rusche 0.2.4

A lightweight Scheme interpreter embeddable in Rust applications
Documentation 
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use std::fmt::{Display, Formatter, Result as FmtResult};

use crate::span::{Loc, Span};

/// The enum that represents a lexical unit of the source code in Rusche.
#[derive(Clone, Debug)]
pub enum Token {
    /// Open parenthesis `(`.
    OpenParen(Loc),

    /// Close parenthesis `)`.
    CloseParen(Loc),

    /// Quote `'`.
    Quote(Loc),

    /// Quasiquote `` ` ``.
    Quasiquote(Loc),

    /// Unquote `,`.
    Unquote(Loc),

    /// Unquote-splicing `,@`.
    UnquoteSplicing(Loc),

    /// A number literal.
    Num(f64, Span),

    /// A string literal.
    Str(String, Span),

    /// A symbol.
    Sym(String, Span),
}

impl Token {
    pub fn span(&self) -> Span {
        match self {
            Token::OpenParen(loc)
            | Token::CloseParen(loc)
            | Token::Quote(loc)
            | Token::Quasiquote(loc)
            | Token::Unquote(loc) => Span::new(*loc, loc.with_column_offset(1)),
            Token::UnquoteSplicing(loc) => Span::new(*loc, loc.with_column_offset(2)),
            Token::Num(_, span) | Token::Str(_, span) | Token::Sym(_, span) => *span,
        }
    }
}

impl PartialEq for Token {
    fn eq(&self, other: &Self) -> bool {
        match (self, other) {
            (Token::OpenParen(_), Token::OpenParen(_)) => true,
            (Token::CloseParen(_), Token::CloseParen(_)) => true,
            (Token::Quote(_), Token::Quote(_)) => true,
            (Token::Quasiquote(_), Token::Quasiquote(_)) => true,
            (Token::Unquote(_), Token::Unquote(_)) => true,
            (Token::UnquoteSplicing(_), Token::UnquoteSplicing(_)) => true,
            (Token::Num(a, _), Token::Num(b, _)) => a == b,
            (Token::Str(a, _), Token::Str(b, _)) => a == b,
            (Token::Sym(a, _), Token::Sym(b, _)) => a == b,
            _ => false,
        }
    }
}

impl Display for Token {
    fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
        match self {
            Token::OpenParen(_) => write!(f, "("),
            Token::CloseParen(_) => write!(f, ")"),
            Token::Quote(_) => write!(f, "'"),
            Token::Quasiquote(_) => write!(f, "`"),
            Token::Unquote(_) => write!(f, ","),
            Token::UnquoteSplicing(_) => write!(f, ",@"),
            Token::Num(value, _) => write!(f, "{}", value),
            Token::Str(text, _) => write!(f, "\"{}\"", text),
            Token::Sym(name, _) => write!(f, "{}", name),
        }
    }
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_span_fixed_len() {
        macro_rules! assert_token_span_length_eq {
            ($length:literal, $token_case:ident) => {
                let span = Token::$token_case(Loc::new(1, 1)).span();
                assert_eq!(span.begin.line, span.end.line);
                assert_eq!($length, span.end.column - span.begin.column);
            };
        }
        assert_token_span_length_eq!(1, OpenParen);
        assert_token_span_length_eq!(1, CloseParen);
        assert_token_span_length_eq!(1, Quote);
        assert_token_span_length_eq!(1, Quasiquote);
        assert_token_span_length_eq!(1, Unquote);
        assert_token_span_length_eq!(2, UnquoteSplicing);
    }

    #[test]
    fn test_display() {
        macro_rules! assert_token_format_eq {
            ($token_case:ident, $formatted:literal) => {
                assert_eq!(
                    format!("{}", Token::$token_case(Loc::new(1, 1))),
                    $formatted
                );
            };
            ($token_case:ident($value:expr), $formatted:literal) => {
                assert_eq!(
                    format!(
                        "{}",
                        Token::$token_case($value, Span::new(Loc::new(1, 1), Loc::new(1, 2)))
                    ),
                    $formatted
                );
            };
        }
        assert_token_format_eq!(CloseParen, ")");
        assert_token_format_eq!(Quote, "'");
        assert_token_format_eq!(Quasiquote, "`");
        assert_token_format_eq!(Unquote, ",");
        assert_token_format_eq!(UnquoteSplicing, ",@");
        assert_token_format_eq!(Num(0.0), "0");
        assert_token_format_eq!(Num(0.5), "0.5");
        assert_token_format_eq!(Num(1.0), "1");
        assert_token_format_eq!(Num(123.456), "123.456");
        assert_token_format_eq!(Num(123.456), "123.456");
        assert_token_format_eq!(Str("str".to_string()), "\"str\"");
        assert_token_format_eq!(Sym("sym".to_string()), "sym");
    }
}