INPUT Execution Codes - Prompting

Execution and translation of the INPUT command was previously described mostly in posts on June 24, 2010, June 25, 2010 and June 27, 2010 . This now needs to be revised since the execution broke the two rules listed at the end on February 16, 2011. Steps 1 and 2 handle issuing the prompt and getting input from the user. This is almost the same as previously defined, which are these codes:

InputBegin    – output default prompt and get input
InputBeginStr – output string prompt and get input
InputBeginTmp – output string prompt, get input and delete temporary string

During execution, the run-time handlers for each of these codes will call a common routine for getting input. This common get input routine can also handle outputting the prompt and can simply use the string on top of the evaluation stack. There will be an argument for whether to output the prompt string on top of the stack and InputBegin will set this argument to false.

There will be another argument for whether to output the default prompt where InputBegin will set this to true and the other two will set to true if the 'Question' sub-code is set (if the prompt string expression was followed by a comma instead of a semicolon).

For InputBeginTmp, the temporary string can be deleted upon returning from the get input routine since it will no longer be needed with the improvement in execution described in last Saturday's posts.