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yyparse returns 0, 1, 2 since ages (accept, reject, memory exhausted). Some of our auxiliary functions such as yy_lac and yyreport_syntax_error also need to return error codes and also use 0, 1, 2. Because it uses yy_lac, yyexpected_tokens also needs to return "problem", "memory exhausted", but in case of success, it needs to return the number of tokens, so it cannot use 1 and 2 as error code. Currently it uses -1 and -2, which is later converted into 1 and 2 as yacc.c expects it. Let's simplify this and use consistently -1 and -2 for auxiliary functions that are not exposed (or not yet exposed) to the user. In particular this will save the user from having to convert yyexpected_tokens's -2 into yyreport_syntax_error's 2: both return -1 or -2. * data/skeletons/yacc.c (yy_lac, yyreport_syntax_error) (yy_lac_stack_realloc): Return -1, -2 for errors instead of 1, 2. Adjust callers. * examples/c/bistromathic/parse.y (yyreport_syntax_error): Do take error codes into account. Issue a syntax error message even if we ran out of memory. * src/parse-gram.y, tests/local.at (yyreport_syntax_error): Adjust.
This directory contains examples of Bison grammar files, sorted per language.
Several of them come from the documentation, which should be installed together with Bison. The URLs are provided for convenience.
These examples come with a README and a Makefile. Not only can they be used to toy with Bison, they can also be starting points for your own grammars.
Please, be sure to read the C examples before looking at the other languages, as these examples are simpler.