PRINT (TAB(10))The first three test the situation of a print function inside a parentheses, internal function and an array or user function, which were caught by adding count stack is not empty check when a print function token is received.
PRINT INT(TAB(10))
PRINT A(TAB(10))
PRINT A+TAB(10)
PRINT TAB(10)+A
In the fourth statement, the error can be caught by checking if the hold stack is not empty (an empty hold stack has only a null token). In this case, an operator will be on top of the hold stack. In fact, this check can replace the count stack is not empty check because the open parentheses, internal function and array/user function will be on top of the hold stack.
The last statement was more difficult to check for - the expression should end after the print function. When the operator was received and checked its operand, a bug occurred because the done stack is empty since the print function didn't get pushed to the done stack. The error should be “expected semicolon, comma or end-of-statement” and point to the operator.
To catch this error, a new end expression state was added. The closing parentheses is received when in binary operator state. After the closing parentheses, the state was left at binary operator since another binary operator is expected (an end of expression token is acceptable as a binary operator). For the end expression state, only operators with the end expression flag are acceptable, which currently include the semicolon, comma and end-of-line tokens – other operators will generate the error.
In resolving these issues, the “invalid used of print function” error did not match the other “expecting...” errors (remember the goal is to help the user by suggesting what is expected at the location of an error). Therefore, this error was changed to be one of the “expecting xxx expression” depending on the current expression type (xxx would be blank, numeric or string).
