reval 0.7.4

Simple Rust expression evaluator
Documentation 
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use unicode_xid::UnicodeXID;

const KEYWORDS: [&str; 17] = [
    "and", "or", "if", "then", "else", "is_some", "is_none", "int", "float", "dec", "true",
    "false", "none", "contains", "in", "to_upper", "to_lower",
];

pub(crate) fn is_reserved_keyword(name: &str) -> bool {
    KEYWORDS.contains(&name)
}

pub(crate) fn is_valid_identifier(name: &str) -> bool {
    let mut chars = name.chars();
    match chars.next() {
        Some(start) => {
            start == '_' || start.is_xid_start() && chars.all(UnicodeXID::is_xid_continue)
        }
        None => false,
    }
}

#[cfg(test)]
mod when_testing_identifier {
    use crate::expr::keywords::is_valid_identifier;

    #[test]
    fn should_allow_leading_underscore() {
        assert!(is_valid_identifier("_id"));
    }

    #[test]
    fn should_allow_leading_letter() {
        assert!(is_valid_identifier("id"));
    }

    #[test]
    fn should_disallow_leading_number() {
        assert!(!is_valid_identifier("1id"));
    }

    #[test]
    fn should_allow_trailing_number() {
        assert!(is_valid_identifier("id1"));
    }
}