Translator – Comma Token Processing

Some comma token processing has already been implemented – commas separating subscripts of arrays or arguments of functions. Commas outside of arrays or functions caused an “unexpected comma” error. This processing needs to be extended to include comma separated multiple assignment statements. Again the current mode will determine how the Translator processes comma operator tokens:

Command: The beginning of a comma separated multiple assignment. The mode will be changed to Comma indicating a comma separated multiple assignment. The comma token is not needed, so it can be deleted. Eventually an assignment operator will be pushed on the hold stack.

Equal: Continuation of a multiple equal assignment statement, so a comma token at this point cause an “unexpected comma in assignment” error.

Comma: Continuation of a comma separated list of a multiple assignment. No further action is needed so the comma token can be deleted.

Expression: Within an expression, so proceeds with the previously implemented comma processing. When the counter stack is empty or the top counter has a zero value, an “unexpected comma in expression” error occurs (changed from “unexpected comma” to differentiate it from the “unexpected comma in in assignment” error).

The comma token has the same low precedence as closing parentheses and assignment operators so most tokens will be removed from the hold stack. Comma tokens are not pushed to the hold stack so they won't be removed. Closing parentheses are also not pushed to the hold stack. And there will never be an assignment operator pushed to the stack before a comma token is processed.

Translator – Equal Token Processing

The Parser returns an equality operator token for an equal. The current mode will determine how the Translator processes equality operator tokens:

Command: The token will be changed to an assignment operator and the mode will be changed to Equal indicating a possible multiple equal assignment and to prevent a comma separated assignment. The assignment operator will be pushed onto the hold stack.

Equal: Continuation of a multiple equal assignment statement. There is already an assignment operator on the hold stack, so this token can be deleted. No further action is needed. During run-time, the single assignment operator will handle multiple variable references.

Comma: The end of a comma separated list of a multiple assignment. The token will be changed to an assignment operator and the mode will be changed to Expression indicating the start of the expression being assigned. The assignment operator will be pushed onto the hold stack.

Expression: Within an expression, equals are equality operators, so the token (already an equality operator) will be processed as a regular binary operator.

The assignment operator will have a very low precedence, which will keep on the hold stack until the end of the statement. Its precedence can be the same as the closing parentheses. The assignment token will be first on the hold stack, so there won't be a closing parentheses token to remove. The closing parentheses only empties the hold stack to an opening parentheses or internal function token (with a lower precedence), so there won't see an assignment token.