Example division and regular expression parser

div_and_reg_parser.kep

var idToken = letter;
var divToken = character('/');
var regularExpressionToken = binds(
    enumeration(
        between(character('/'), character('/'),
            eager <| many(letter)),
        optional('', letter)),
    \body, flag ->
        always('/' + body +'/' + flag + ')'));


expr = rec <| \expr -> {
    var id = idToken;
    
    var regExp = bind(regularExpressionToken,
        \r -> always( '(' + r + ')' ));
    
    var primaryExpression = either(regExp, id);
    
    var div = binds(
        enumeration(
            attempt <| then(
                primaryExpression,
                divToken),
            expr),
        \l, r -> always( '(' + l + ' / ' + r + ')' ));
    
    return either(
        div,
        primaryExpression);
};