Translator – Token Handlers (Implementation)

A TokenHandler typedef was needed to define the pointer to token handler function. I was not able to define the function pointer directly on the variables. This always proves difficult with more complex types, especially involving pointers. Fortunately, using typedef simplifies the issue. Here is the definition that was inserted before the TableEntry class:

class Translator;   // forward reference to Translator class
typedef TokenStatus (*TokenHandler)(Translator &p, Token *&token);

The TokenHandler type definition is then used for defining an token handler function pointers. Each of the token handlers were created using the existing code in the switch statement, where the code was modified to add the Translator pointer in front of all the Translator variables and the Translator scope (Translator::) was added to the Translator enumeration values.

The code that handles operators (which was after the switch statement for the special codes) was also put into a handler function. This greatly simplified the code at the end of the add token function. For processing the token, the temporary token handler function pointer is set to the code's table entry value. If the value is not set (is NULL), then the temporary pointer is set to the default operand token handler function. The function is called using the temporary pointer and it's status return value is immediately returned.

The program was compiled several times during the making of the changes. I got tired of running of the test cases (to output is redirected to a file in the base directory) and comparing to the official test output files (in the test directory), so I wrote a MSYS (bash) script to do it automatically and check all the test cases. An equivalent Windows batch file was also written, but does not work near as nice. Both will be included in the next release.