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Textual Positions of Tokens
If you are using the `@N'-feature (Note: Special Features for Use in
Actions.) 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. 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.
The data type of `yylloc' has the name `YYLTYPE'.
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