Textual Positions of Tokens
---------------------------

   If you are using the `@N'-feature (*note Special Features for Use in
Actions: Action Features.) 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'.