# Parser
## Explanation of options:
```cpp
// Bison version
%require "3.0.4"

// skeleton program to be used as parser
%skeleton "lalr1.cc" 

// tells bison to generate a header file
%defines 

// where the parser will live (in what namespace)
%define api.prefix {yy} 

// the name of parser class
%define api.parser.class {Parser} 

/* it will generate a location class which can be used in your lexer */
%locations

/* use the constructor for each token, and make_TOKENNAME functions will be generated */
%define api.token.constructor 

/* use the variant type for $1~$n and $$ those variables */
%define api.value.type variant

%define parse.trace
%define parse.error verbose
```