parsley 0.10.0

An implementation of Scheme
Documentation 
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pub fn is_atom_char(c: char) -> bool {
    !c.is_whitespace()
        && !c.is_control()
        && c != '('
        && c != ')'
        && c != '['
        && c != ']'
        && c != '{'
        && c != '}'
}

pub fn is_symbol_char(c: char) -> bool {
    c.is_alphanumeric()
        || c == '-'
        || c == '_'
        || c == '?'
        || c == '!'
        || c == '*'
        || c == '+'
        || c == '/'
        || c == '='
        || c == '<'
        || c == '>'
}

pub fn find_closing_delim(
    s: impl Iterator<Item = char>,
    d_plus: char,
    d_minus: char,
) -> Option<usize> {
    let mut depth = 0;

    for (idx, c) in s.enumerate() {
        if d_plus == d_minus {
            if c == d_plus {
                depth = !depth;
            }
        } else {
            match c {
                x if x == d_plus => depth += 1,
                x if x == d_minus => depth -= 1,
                _ => (),
            }
        }

        if depth == 0 {
            return Some(idx);
        }
    }

    None
}