pub fn lexer() -> BoxedParser<'static, char, Vec<(Token, Span)>, Simple<char>> {
    let ident = text::ident().labelled("ident");

    let number = {
        // We only support decimal literals for now, not the full scope of numbers.
        // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Lexical_grammar#numeric_literals
        let digit = one_of("0123456789");
        let digits = digit.then_ignore(just('_').or_not()).repeated().at_least(1);
        let sign = just('-')
            .or(just('+'))
            .map(|c| c.to_string())
            .or_not()
            .map(Option::unwrap_or_default);
        let integer = sign.chain(digits.clone());

        let fraction = just('.')
            .chain(digits.clone())
            .or_not()
            .map(Option::unwrap_or_default);
        let exponent = just('e')
            .or(just('E'))
            .chain(sign.chain(digits))
            .or_not()
            .map(Option::unwrap_or_default);
        integer
            .chain::<char, _, _>(fraction)
            .chain::<char, _, _>(exponent)
            .collect()
    };

    let string = {
        let normal_char = filter(|&c: &char| c != '"' && c != '\\' && !c.is_control());
        let hex_digit = filter(|&c: &char| c.is_ascii_hexdigit());
        let control_char = just('\\')
            .chain(
                one_of("\"\\/bfnrt")
                    .map(|c| vec![c])
                    .or(just('u').chain(hex_digit.repeated().at_least(4).at_most(4))),
            )
            .collect::<String>();
        let chars = normal_char
            .map(|c| c.to_string())
            .or(control_char)
            .repeated()
            .collect();
        just('"').ignore_then(chars).then_ignore(just('"'))
    };

    let expr = just('`')
        .ignore_then(take_until(just('`')))
        .map(|(s, _)| s)
        .collect()
        .labelled("expr");

    let ctrl = choice::<_, Simple<char>>((
        just::<_, _, Simple<char>>(":-"),
        just::<_, _, Simple<char>>("("),
        just::<_, _, Simple<char>>(")"),
        just::<_, _, Simple<char>>("["),
        just::<_, _, Simple<char>>("]"),
        just::<_, _, Simple<char>>("{"),
        just::<_, _, Simple<char>>("}"),
        just::<_, _, Simple<char>>(":"),
        just::<_, _, Simple<char>>("."),
        just::<_, _, Simple<char>>(","),
        just::<_, _, Simple<char>>("="),
    ));

    let token = choice((
        ident.map(Token::Ident),
        number.map(Token::Number),
        string.map(Token::String),
        expr.map(Token::Expr),
        ctrl.map(Token::Ctrl),
    ))
    .boxed()
    .recover_with(skip_then_retry_until([]));

    let comments = {
        let single_line = just("//").then_ignore(take_until(text::newline()));
        let multi_line = just("/*").then_ignore(take_until(just("*/")));
        single_line
            .or(multi_line)
            .padded()
            .repeated()
            .map_err(|e: Simple<char>| Simple::custom(e.span(), "Not a valid comment"))
    };

    token
        .padded()
        .padded_by(comments)
        .map_with_span(|tok, span| (tok, span))
        .repeated()
        .boxed()
}
/// Construct a parser combinator for lexical analysis (stage 1).
///
/// If possible, prefer to use the higher-level `Grammar` API directly, rather
/// than this low-level implementation of a parser combinator.
Construct a parser combinator for lexical analysis (stage 1).
If possible, prefer to use the higher-level `Grammar` API directly, rather
than this low-level implementation of a parser combinator.
Construct a parser combinator for lexical analysis ( stage 1 ) . If possible prefer to use the higher - level ` Grammar ` API directly rather than this low - level implementation of a parser combinator .
pub fn lexer() -> BoxedParser<'static, char, Vec<(Token, Span)>, Simple<char>> {
    let ident = text::ident().labelled("ident");
    let number = {
        // We only support decimal literals for now, not the full scope of numbers.
        // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Lexical_grammar#numeric_literals
        let digit = one_of("0123456789");
        let digits = digit.then_ignore(just('_').or_not()).repeated().at_least(1);
        let sign = just('-')
            .or(just('+'))
            .map(|c| c.to_string())
            .or_not()
            .map(Option::unwrap_or_default);
        let integer = sign.chain(digits.clone());
        let fraction = just('.')
            .chain(digits.clone())
            .or_not()
            .map(Option::unwrap_or_default);
        let exponent = just('e')
            .or(just('E'))
            .chain(sign.chain(digits))
            .or_not()
            .map(Option::unwrap_or_default);
        integer
            .chain::<char, _, _>(fraction)
            .chain::<char, _, _>(exponent)
            .collect()
    };
    let string = {
        let normal_char = filter(|&c: &char| c != '"' && c != '\\' && !c.is_control());
        let hex_digit = filter(|&c: &char| c.is_ascii_hexdigit());
        let control_char = just('\\')
            .chain(
                one_of("\"\\/bfnrt")
                    .map(|c| vec![c])
                    .or(just('u').chain(hex_digit.repeated().at_least(4).at_most(4))),
            )
            .collect::<String>();
        let chars = normal_char
            .map(|c| c.to_string())
            .or(control_char)
            .repeated()
            .collect();
        just('"').ignore_then(chars).then_ignore(just('"'))
    };
    let expr = just('`')
        .ignore_then(take_until(just('`')))
        .map(|(s, _)| s)
        .collect()
        .labelled("expr");
    let ctrl = choice::<_, Simple<char>>((
        just::<_, _, Simple<char>>(":-"),
        just::<_, _, Simple<char>>("("),
        just::<_, _, Simple<char>>(")"),
        just::<_, _, Simple<char>>("["),
        just::<_, _, Simple<char>>("]"),
        just::<_, _, Simple<char>>("{"),
        just::<_, _, Simple<char>>("}"),
        just::<_, _, Simple<char>>(":"),
        just::<_, _, Simple<char>>("."),
        just::<_, _, Simple<char>>(","),
        just::<_, _, Simple<char>>("="),
    ));
    let token = choice((
        ident.map(Token::Ident),
        number.map(Token::Number),
        string.map(Token::String),
        expr.map(Token::Expr),
        ctrl.map(Token::Ctrl),
    ))
    .boxed()
    .recover_with(skip_then_retry_until([]));
    let comments = {
        let single_line = just("//").then_ignore(take_until(text::newline()));
        let multi_line = just("/*").then_ignore(take_until(just("*/")));
        single_line
            .or(multi_line)
            .padded()
            .repeated()
            .map_err(|e: Simple<char>| Simple::custom(e.span(), "Not a valid comment"))
    };
    token
        .padded()
        .padded_by(comments)
        .map_with_span(|tok, span| (tok, span))
        .repeated()
        .boxed()
}
pub fn lexer ( ) -> BoxedParser < ' static , char , Vec < ( Token , Span ) > , Simple < char > > { let ident = text :: ident ( ) . labelled ( " " ) ; let number = { // We only support decimal literals for now, not the full scope of numbers. // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Lexical_grammar#numeric_literals let digit = one_of ( " " ) ; let digits = digit . then_ignore ( just ( '_' ) . or_not ( ) ) . repeated ( ) . at_least ( 1 ) ; let sign = just ( '-' ) . or ( just ( '+' ) ) . map ( | c | c . to_string ( ) ) . or_not ( ) . map ( Option :: unwrap_or_default ) ; let integer = sign . chain ( digits . clone ( ) ) ; let fraction = just ( '.' ) . chain ( digits . clone ( ) ) . or_not ( ) . map ( Option :: unwrap_or_default ) ; let exponent = just ( 'e' ) . or ( just ( 'E' ) ) . chain ( sign . chain ( digits ) ) . or_not ( ) . map ( Option :: unwrap_or_default ) ; integer . chain :: < char , _ , _ > ( fraction ) . chain :: < char , _ , _ > ( exponent ) . collect ( ) } ; let string = { let normal_char = filter ( | & c : & char | c != '"' && c != '\\' && ! c . is_control ( ) ) ; let hex_digit = filter ( | & c : & char | c . is_ascii_hexdigit ( ) ) ; let control_char = just ( '\\' ) . chain ( one_of ( " \" \\ " ) . map ( | c | vec ! [ c ] ) . or ( just ( 'u' ) . chain ( hex_digit . repeated ( ) . at_least ( 4 ) . at_most ( 4 ) ) ) , ) . collect :: < String > ( ) ; let chars = normal_char . map ( | c | c . to_string ( ) ) . or ( control_char ) . repeated ( ) . collect ( ) ; just ( '"' ) . ignore_then ( chars ) . then_ignore ( just ( '"' ) ) } ; let expr = just ( '`' ) . ignore_then ( take_until ( just ( '`' ) ) ) . map ( | ( s , _ ) | s ) . collect ( ) . labelled ( " " ) ; let ctrl = choice :: < _ , Simple < char > > ( ( just :: < _ , _ , Simple < char > > ( " " ) , just :: < _ , _ , Simple < char > > ( " " ) , just :: < _ , _ , Simple < char > > ( " " ) , just :: < _ , _ , Simple < char > > ( " " ) , just :: < _ , _ , Simple < char > > ( " " ) , just :: < _ , _ , Simple < char > > ( " " ) , just :: < _ , _ , Simple < char > > ( " " ) , just :: < _ , _ , Simple < char > > ( " " ) , just :: < _ , _ , Simple < char > > ( " " ) , just :: < _ , _ , Simple < char > > ( " " ) , just :: < _ , _ , Simple < char > > ( " " ) , ) ) ; let token = choice ( ( ident . map ( Token :: Ident ) , number . map ( Token :: Number ) , string . map ( Token :: String ) , expr . map ( Token :: Expr ) , ctrl . map ( Token :: Ctrl ) , ) ) . boxed ( ) . recover_with ( skip_then_retry_until ( [ ] ) ) ; let comments = { let single_line = just ( " " ) . then_ignore ( take_until ( text :: newline ( ) ) ) ; let multi_line = just ( " " ) . then_ignore ( take_until ( just ( " " ) ) ) ; single_line . or ( multi_line ) . padded ( ) . repeated ( ) . map_err ( | e : Simple < char > | Simple :: custom ( e . span ( ) , " " ) ) } ; token . padded ( ) . padded_by ( comments ) . map_with_span ( | tok , span | ( tok , span ) ) . repeated ( ) . boxed ( ) }
Construct a parser combinator for lexical analysis (stage 1).
Construct a parser combinator for lexical analysis ( stage 1 ) .