Translator – Debugging - Sub-String Assignments (III)

The next issue is the output of the correct error messages. Consider these expressions and the current error messages (underlined tokens indicate where the error is pointing):

RIGHT$(LEFT$(A$,1),2) = B$  item cannot be assigned
RIGHT$(A,2) = B$  expected string expression
RIGHT$(A%,2) = B$  expected string expression
RIGHT$(A$+B$,2) = C$  item cannot be assigned

The desired error message is “expected string variable” for the first three statement and “expected comma” for the fourth statement. The section that receives an internal function token and checks for a sub-string function in an assignment was previously corrected to accept sub-string functions and set their reference flag (so that the reference flag of the first operand is checked).

An additional check was needed to catch a second sub-string function. Checking if there is a token on top of the hold stack with its reference flag set is sufficient. This condition only occurs when there is a sub-string assignment. However, this check is only be performed when on the first operand.

When the find code routine found an operand with an incorrect data type, it was returning “expected <datatype> expression” errors. This was modified that if the reference flag of the token is set, then an expected variable error is returned. However, for strings, the “expected string item for assignment” error was returned to indicate sub-string assignments are allowed. But if already inside the sub-string function, this needed to be the “expected string variable” error.

For the last statement, a check was added to the operator section in the add token routine, the same if the token on top of the hold stack has its reference flag set on the first operand check, if the token is not a comma, then an “expected comma” error is returned.