Recreator – Sub-String Assignments

Translated sub-string assignments (previously described on July 14) consist of the string reference, followed by the expressions of the arguments of the sub-string function with the assign sub-string code.  This is the same form as when these functions appear in expressions, so sub-strings can be recreated the same way.  This is not the case with multiple sub-string assignments where the sub-string assign codes are all at the end of the translated statement with special assign keep codes except for the final code.

At run time, after popping the value to assign and assignment the value, the assign keep codes push the value back to the stack for the next assignment.  The final non-keep assignment just pops the value off of the stack.  The recreation of multiple sub-string assignments works similarly.  The assign keep code will pop the recreated string of the value expression to assign.  A sub-string assign keep code recreates the sub-string as a function and push the result back to the stack.  For all assign keep codes, the reference string is popped, the current separator is added followed by the value string.  This string is pushed back to the stack.

For the final non-keep assign code, the LET keyword is appended to the output string if the assign code has the option sub-code.  The value string is popped from the stack, which will also contain the other references in a multiple assignment statement.  The string of the final reference is popped and appended to the output string.  Finally the value string is appended to the output string.

Implementation

A separator character member variable was added to the recreator class with access functions for getting the separator character, checking if it is set (not the null character), clearing it (setting it to the null character), and setting it.

The new assign string recreate function contains a local string variable and starts by checking if the separator character is not set.  An unset separator indicates the first and maybe only reference. For the first reference, the string is set to the assignment operator (an equal) surrounded by spaces and the separator is set to a comma.  If the separator is set, then the string is set to it (which is a comma) plus a space.  The string on top of the holding stack is popped and appended to the string.

If the assignment token has the sub-string flag set, then the code of the original sub-string function is obtained.  This was accomplished by making the original sub-string function code the second associated code in all the table entries of the assign keep and non-keep sub-string codes.  The name and the operand count is obtained for the original sub-string function code and the push with operands routine is called to process the arguments of the sub-string function.  The resulting string is left on top of the holding stack.

If the assignment code is a keep code (determined if the second associated code index is zero, which is only the case for the keep codes), the value string with the separator and other references prefixed is appended to the string on top of the holding stack.  Otherwise the assignment code is the end of the statement.  The let recreate function is called to append the LET keyword if the option sub-code is set.  The last reference is popped from the holding stack, appended to the output string, and the string with the rest of the references, separators and value is appended to the output string.  The separator is cleared for the next command.

All of the translator assignment tests (#1 through #5) are all now recreated corrected except for a single PRINT statement in test #5 (since the PRINT recreation has not been implemented yet).

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