Translator – PRINT and Assign Restructuring

Only the PRINT and Assign commands commands are implemented so far, which were restructured where the related code for these commands contained in the comma and semicolon tokens was relocated into the command handlers. These token handlers will now call the command handlers just like the end-of-line token handler does. A switch was added to the command handlers on the code of the token passed in. Previously this token was only the end-of-line token.

The code from the end-of-line token handler that called a command handler was moved to a new call command handler routine that does as described in the last post except at the beginning, a check was added if the command stack is empty. This condition can occur in an assignment statement before a comma or equal token has been received. A null token status will be returned for the caller to report the appropriate error.

For the comma token handler, a null token status can only occur in expression only test mode because this mode does not put a command on the command stack. For the semicolon token handler, a null token status can occur if the semicolon is at the beginning of the line (where a command is expected) or after a variable (where a comma or equal is expected). The same conditions don't occur at a comma because there are specific checks depending on the current mode (command, assignment list or expression), where as the semicolon doesn't check the mode.

For the PRINT command handler, the code related code was moved moved from these token handlers into the appropriate cases of the switch. Since no other tokens are currently expected, the default case was set to return an unexpected token bug error.

The Assign Command handler only expects an end-of-line token, so for the default case, the assignment list mode returns a equal or comma expected error and expression mode returns an operator or end of statement expected error when expecting a binary operator or a numeric or string expression expected error when expecting an operand. Before returning the error, the command item token needed to be set to the token passed in to point the error to the token causing the error.

A few other issues were discovered after the code was restructured and tested...