Translator – Data Type Matching

When determining which code (main or associated) to use from the operand's data types, there can be an exact match, no match or a convertible match. A convertible match can be made to be an exact match when conversion code(s) are added after the operand that doesn't match exactly. An exact match is preferred.

There will be a match routine that will determine the type of match there is between the current operand's data type(s) and a code's required data type(s). In additional to returning the type of match found (exact, none, or convertible), the conversion codes needed for each operand or Null if a particular operand does not need conversion will also be returned.

This match routine will use an table holding the conversion codes for each possible operand (have) data type and required (need) data type pairs. For the pairs where the two data types are the same, the conversion code will be set to the Null code. For the pairs with an Integer or Double vs. a String, the conversion code will be set to an Invalid code. The only pairs with actual conversion codes are the have Integer need Double pair (CvtDbl) and the have Double need Integer pair (CvtInt).

The routine for finding the code for the data types of the operand(s) will be called from both the add operator routine and the internal function routine (after the number of arguments is checked). The operands will be pulled off of the done stack to get their data types. Using the match routine, the operands will be checked against the main code for a data type match. If an exact match is found, then no further action is needed. If a convertible match was found, the main code is saved in case no further exact match is found.

When the main code is not an exact match, each of the associated codes (if any) of the main code table entry are checked for a match. For each, if an exact match is found, then no further action is needed. If a convertible match was found, the associated code is saved in case no further exact match is found.

If a convertible match was found, then the token's code is changed and the conversion codes are inserted into the output list after the operands. If no match was found, then one of three “expected <data type>” errors (one for each data type) will be reported against the first operand with an Invalid code in the conversion codes returned from the match routine.