Translator – More Expression Type Debugging

The next problem was occurring when there was an unexpected operand when an operator, comma or closing parentheses was expected (for example: Z$=MID$(A$,B C). This was only occurring for functions with multiple arguments (ASC, MID$ and INSTR) when at the last argument of the shorter form. The “expected operator or closing parentheses” error was produced, but a comma could follow for the optional argument.

A checked was added to the parentheses status routine when at the last argument. If the function has the Multiple flag set, indicating there is another form with more arguments, then the “expected operator, comma or closing parentheses” error is produced instead.

One problem remained, the statement Z$=MID$(A$,B, produced an “expected string expression” at the end of the line where it should have been an “expected numeric expression” error. The problem also occurred on the last optional argument of the INSTR and ASC functions. The problem was caused because the top of the count stack contained the index to the first form of these functions instead of to the second form with the optional argument.

When the code went to get the argument's data type, it ran of the end off the operand data type array incorrectly picking up a string data type. The coding error was on the line that incremented the index of the token on the hold stack to the next form of the function and assigned it to the index on top of the count stack. A post-increment C operator was used instead of the pre-increment operator and the index on the count stack was not actually changed.

Now all the test statements in the Eleventh Translator test are working (and on expected error needed to be corrected on the Third test because of the last fixed – it was missed previously). On to the Twelfth (more error statements) test...