Parser C-Language Interface
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The Bison parser is actually a C function named `yyparse'. Here we
describe the interface conventions of `yyparse' and the other functions
that it needs to use.
Keep in mind that the parser uses many C identifiers starting with
`yy' and `YY' for internal purposes. If you use such an identifier
(aside from those in this manual) in an action or in additional C code
in the grammar file, you are likely to run into trouble.