Translator – Simple Expressions (Problem Solved)

I suspected the problem with the expression “A-B” had something to do with the fact the “-” could be a unary operator (the expression “A+B” worked fine). The first problem discovered was that the Parser was seeing this as the Auto command; “-” was valid for the start of a line number range, but the “B” was not valid, so an “unexpected error” was returned. However, the Translator test code did not check for an Error token and passed it to the Translator, which did not know what to do with it. Therefore, the test code was modified to output a Parser error and terminate the processing of the input line.

To correct the problem with this expression being treated as a invalid immediate command, this error was temporarily removed. Temporary because no valid BASIC line would have just “A-B” on it, but for now only expressions are being tested. Most of the Translator was handling the “-” as a binary operator correctly until it got to the add operator routine. There is a check that only pops one operand from the done stack for a unary operator and it was this check that was wrong.

To simplify the check for a unary operator (which should check if the Table entry code is the same as the unary code, not if the unary code is not set to Null), an is_unary_operator() function was added to the Table class that does this check. This should eliminate possible future dumb coding errors. Now it's time to package this up and release it...