3.6.1 Data Type of Locations

Defining a data type for locations is much simpler than for semantic values, since all tokens and groupings always use the same type.

You can specify the type of locations by defining a macro called YYLTYPE, just as you can specify the semantic value type by defining a YYSTYPE macro (see section Data Types of Semantic Values). When YYLTYPE is not defined, Bison uses a default structure type with four members:

typedef struct YYLTYPE
{
  int first_line;
  int first_column;
  int last_line;
  int last_column;
} YYLTYPE;

At the beginning of the parsing, Bison initializes all these fields to 1 for yylloc.