bison

When there is a shift/reduce conflict in Yacc/Bison, is it possible to force the conflict to be solved exactly as you want? In other words: is it possible explicitly force it to prioritize the shift or the reduce? For what I have read, if you are happy with the default resolution you can tell the generator to not complain about it . I really don't like this because it is obfuscating your rational choice. Another option is to rewrite the grammar to fix the issue. I don't know if this is always possible and often this makes it much harder to understand. Finally, I have read the precedence rules

I'm trying to write my first parser with Flex & Bison. When parsing numbers, I'm trying to save their values into the yylval structure. The problem is, yylval is null when the lexer reaches a number, which causes a segmentation fault. (Related point of confusion: why is it that in most Flex examples (e.g. here ), yylval is a structure, rather than a pointer to a structure? I couldn't get yylval to be recognized in test.l without %option bison-bridge , and that option made yylval a pointer. Also, I tried initializing yylval in main of test.y, but yylval = malloc(...) gives a type mismatch-- as

I have a problem with compilation of my code: Flex: %{ #include "lista4.tab.hpp" #include <stdlib.h> extern int yylex(); %} %% "=" {return EQ;} "!=" {return NE;} "<" {return LT;} ">" {return GT;} ":=" {return ASSIGN;} ";" {return SEMICOLON;} "IF" {return IF;} "THEN"{return THEN;} "END" {return END;} [_a-z]+ {yylval.text = strdup(yytext); return IDENTIFIER;} [ \t]+ [0-9]+ { yylval.var = atoi (yytext); return NUMBER; } [-+/^*'%'()] { return *yytext; } \n return RESULT; %% Bison: %{ extern "C" { int yyparse(); int yylex(void); void yyerror(char *s){} int yywrap(void){return 1;} } #include

What is the best way to handle multiple Flex/Bison parsers inside a project? I wrote a parser and now I need a second one in the same project. So far in the third section of parser1.y I inserted the main(..) method and called yyparse from there. What I want to obtain is having two different parsers ( parser1.y and parser2.y ) and be able to use them from an external function (let's assume main in main.cpp ). Which precautions should I use to export yyparse functions outside .y files and how should I handle two parsers? PS. I'm using g++ to compile but not the C++ versions of Flex and Bison and

I am trying to translate my .spl file into a C file (because there is no compiler). I have an example "Hello World" .spl file, and I have downloaded the Shakespeare Programming Language .tar and extracted it, but I have no idea what to do next. I can't seem to find instructions in any documentation. Can anyone help? Edit: When I type make -f "Makefile" , I get the following output: bison --verbose -d grammar.y gcc -O2 -Wall -c grammar.tab.c gcc -O2 -Wall -c makescanner.c gcc makescanner.o -O2 -Wall -o makescanner ./makescanner include > scanner.l flex -Cem -t scanner.l > scanner.c scanner.l

I'm trying to parse C-style multi-line comments in my flex (.l) file: %s ML_COMMENT %% ... <INITIAL>"/*" BEGIN(ML_COMMENT); <ML_COMMENT>"*/" BEGIN(INITIAL); <ML_COMMENT>[.\n]+ { } I'm not returning any token and my grammar (.y) doesn't address comments in any way. When I run my executable, I get a parse error: $ ./a.out /* abc def Parse error: parse error $ echo "/* foo */" | ./a.out Parse error: parse error (My yyerror function does a printf("Parse error: %s\n"), which is where the first half of the redundant error message comes from). I can see why the second example fails since the entirety