Temporary Strings – Design

During run-time the string operator and internal string functions need to delete the character array of a temporary string operand, but not of a reference string. Figuring out the design for temporary strings has proven difficult. The ultimate goal is fast execution at run-time. Two solutions were considered.

The first solution (easy to implement), would be to add a temporary flag to the String class. After an operation was finished with an operand, it would be deleted. If the temporary flag is set, then the character array would be deleted, otherwise, no action is taken. This was not desirable because the run-time would need to check for the temporary string flag, adding to execution time.

The other solution (more involved to implement) would not require checks for temporary strings during run-time. This solution is desirable, and will require separate codes for whether the operands are reference strings or a temporary strings.

For instance, the CatStr code would handle the case where both operands are reference strings. There would be three associated codes to the CatStr main code, one for when the first operand is a temporary string and second operand is a reference string (CatStrT1), one for when the first operand is a reference string and the second is a temporary (CatStrT2), and one for when both operands are temporary strings (CatStrTT). These associated codes would delete the temporary operand(s) after the concatenation.

Unfortunately, the presence of temporary strings is not necessary known during translation. The reason being that identifiers could be variables, array elements, or user functions. Variables and array elements produce reference strings. However, user functions like internal functions produce temporary strings except within a user function where the function name will be used as a variable holding the value that will be returned by the function.

Remember that the Translator does not determine what the identifier is – this job is left to the Encoder, which has access to the Dictionary. The Dictionary will contain all the identifiers and what they are. Next, what changes are required in the Translator for temporary strings...