Reading input
User must provide input to parser by implementing NextToken() method:
Procedure should return next input token or error code. Error code should be one of predefined error codes, or a custom user-defined code with value below USER_FIRST. If token has associated value, this value should be placed in provided valueData.
Implementation of NextToken method is controlled by Parser.Code.NextTokenImpl option.
When option is set to UserCode code for NextToken() method body must be provided in parser_next_token block like this:
return someLexer.NextToken();
}
When option is set to Virtual NextToken() method is declared virtual with empty body. User must override this method in a subclass. This approach does not require placement of user code inside Alpag file.
When option is set to UserCodeInline method is not declared at all, and user code is placed directly inside body of parser procedure.
In earlier versions of Alpag parser_next_token code section was called next_token. This old name is not supported anymore.