Translator – Unary Operator Problem

While testing the negative constant changes, a new problem was discovered with unary operators, specifically this statement:

A = ---B

Which produced a “done stack empty” bug error at the first negation token. The problem occurred because the second negation operator forced the first negation operator from the hold stack because it was greater or equal precedence, and when checking the operand of the first negation operator, there was nothing on the done stack. Here and some additional examples:

A = B*-C
A = B^-C

The first statement translated correctly because negation is higher precedence than multiplication leaving multiplication on the hold stack. However, the second statement failed because negation is lower precedence than exponentiation forcing exponentiation from the hold stack but with only one operand on the done stack generating the done stack empty bug error. A new rule was needed for unary operators.

Basically, unary operators should not force any tokens (unary operators, binary operators, arrays, or functions) from the hold stack regardless of their precedence because not all of their operands have been received yet (the negate and its operand will be their operand and it has not been fully received yet). As currently implemented, other non-unary operators should still force unary operators from the done stack if the unary operator has higher precedence.

The check to force tokens from the hold stack was changed to if the precedence of the operator on the hold stack is higher than the current operator and if the current token is not a unary operator. Unary operators will now not force other tokens from the hold stack, but other tokens will still force unary operators from the hold stack if higher in precedence. While testing this change, a curious result was produced from one of the test statements...