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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;
While default locations represent a range in the source file(s), this is not a requirement. It could be a single point or just a line number, or even more complex structures.
When YYLTYPE
is not defined, at the beginning of the parsing, Bison
initializes all these fields to 1 for yylloc
. To initialize
yylloc
with a custom location type (or to chose a different
initialization), use the %initial-action
directive. See section Performing Actions before Parsing.