lisp_eval_should_be '(as-number "42")' '42' 'as-number'
lisp_eval_should_be '(as-number "xlerb")' '()' 'as-number not number makes error'
lisp_eval_should_be '(as-number true)' '()' 'as-number not string makes error'

    else if(car == _symbol("as-number"))
        return _as_number(_eval3(_cadr(form), env, env, d+1))

function _as_number(val) {
    if(_TYPE[val] == "s") {
        # copypasted from reader.awk.
        if(_STRING[val] ~ /^(\+|-)?([0-9]+\.)?[0-9]+([eE][+-]?[0-9]+)?$/) {
            return _number(_STRING[val])
        } else {
            logg_err("_as_number", "this does not appear to be a number: " awkescape(_STRING[val]))
            return _nil()
        }
    } else {
        logg_err("_as_number", "as-number value should be a string")
        return _nil()
    }
}

(defintrinsic as-number (s))

    _symbol("as-number")