Translator – Commands and Precedence

In the translated RPN list, the command token will generally end up at the end of the statement. To accomplish this, the command tokens need to be saved until the rest of the statement is translated. The best place to save the command tokens is on the hold stack with a very low precedence to keep them on the stack until the end of statement.

The appropriate precedence of commands would appear to be the same as the EOL token, so that when the EOL token is processed, the command tokens will be emptied from the stack. This implies that commands could empty other commands, but generally, this will not occur except for multiple keyword commands (like the IF-THEN-ELSE and FOR-TO-STEP commands).

The EOL token currently has the same precedence as assignment, closing parentheses, and comma tokens. It makes sense for assignment and commands to be the same precedence because assignment is technically a command. An assignment will never empty a command from the hold stack because the Translator never receives an assignment operator. An equals token is received as an equality operator, which has a higher precedence, so it won't empty any lower precedence commands. It's only after the stack emptying that an equals token may be changed to an assignment token.

Closing parentheses and comma tokens, being the same precedence, will empty all tokens with higher or same precedence, which is a problem, since command tokens will be the same precedence. This is currently not an issue because:

1. An EOL token is not pushed onto the hold stack and therefore can't be emptied by a closing parentheses or comma.
2. An assignment operator is not on the hold stack when a multiple assignment comma is processed, so the comma won't empty an assignment token.
3. An assignment token is on the hold stack when a comma is processed within an array or function – the lower precedence array or function token will be on the stack before the assignment token, so it won't empty the assignment token.
4. An assignment token is on the hold stack when a comma is processed not within an array or function (though possibly after an opening parentheses) – this is an unexpected comma and an error occurs.
5. A closing parentheses may empty an assignment token from the stack, but since no opening parentheses, array or function token is found on the stack, an error occurs.

This means the precedence of closing parentheses and comma tokens need to be increased above assignment and command tokens so that they do not empty them from the hold stack, but below any other operator. Closing parentheses and comma tokens are never pushed onto the hold stack, so there is no worry about them being emptied from the hold stack by an EOL or command token (an assignment token never empties the hold stack).