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If you are using the ‘@n’-feature (see Tracking Locations) in actions to keep track of the textual locations
of tokens and groupings, then you must provide this information in
yylex
. The function yyparse
expects to find the textual
location of a token just parsed in the global variable yylloc
.
So yylex
must store the proper data in that variable.
By default, the value of yylloc
is a structure and you need only
initialize the members that are going to be used by the actions. The
four members are called first_line
, first_column
,
last_line
and last_column
. Note that the use of this
feature makes the parser noticeably slower.