Calling The Parser

First, how the Parser will be used needs to be defined. Since it is a class, it needs to be instanced:

    Parser parser;

The constructor doesn't need to do anything. The input line will be inputted from the user, initially from a prompt like BASIC interpreters, and later from a screen editor. In either case it will be a standard C zero-terminated character array. This array needs to be initially fed to the Parser, something like:

    char *input;
    ...
    parser.start(input);

The start function will initialize internal variables in preparation for parsing the line into tokens. Tokens are then obtained from the parser:

    Token *token;
    ...
    while ((token = parser.get_token()) != NULL)
    {
        ... process token here ...
    }

The Parser will also detect some syntax errors. To keeps things simple, a special Error token type will be added to the token type enumeration. For these error tokens, the column will be set to where the error was detected, and the string will contain the error message.

When the end of the line is reached, a NULL token pointer will be returned. The Parser will allocate the tokens, but it will up to the caller to delete the tokens. There will be a destructor for the Token structure that will delete the String contained within if set. This will eventually be handled by the Encoder once the tokens have been converted to the internal code. The Translator will process the tokens, possibly modifying them as the line is processed (more on this modifying later when the Translator is developed).