Problem with a simple grammar
Hello,
I have a simple bison file summarizes as
#define YYSTYPE const char*
%token NUMBER A TEXT
%%
stmt: expr /* append a copy of prg to a list */
| stmt expr /* append a copy of prg to a list */
;
expr: NUMBER TEXT A TEXT {
prg.num = atoi($1);
prg.enu = $1; prg.E += $2; /* as C++ strings */
prg.A = $3; prg.A += $4;
}
;
where "prg" is a struct with an int and 2 string members.
When I run the program I got all members of prg having the same semantic
value, i.e. all with the last string ($4). So I changed to
expr: NUMBER {prg.num = atoi($1); prg.enu = $1;}
TEXT { prg.enu += $3 /* as C++ strings */ }
A {prg.A = $5;}
TEXT {prg.A += $7;}
;
and then works as it should be. So the question is: why doesn't the first one
work?
thanks
PS. I have to use bison 1.24 so you may not be able to help me.
___
Help-bison@gnu.org http://lists.gnu.org/mailman/listinfo/help-bison
Re: Problem with a simple grammar
I have a simple bison file summarizes as #define YYSTYPE const char* ... When I run the program I got all members of prg having the same semantic value, i.e. all with the last string ($4). This is one of the most frequently asked question on this list: You forget to make copies of the strings in your lexer. Thus you only get a pointer into a buffer, as you work with pointers. PS. I have to use bison 1.24 so you may not be able to help me. This is rather old; the latest release is 2.0 -- Hans Aberg ___ Help-bison@gnu.org http://lists.gnu.org/mailman/listinfo/help-bison
Re: Problem with a simple grammar
> >I have a simple bison file summarizes as > > > >#define YYSTYPE const char* > > ... > > >When I run the program I got all members of prg having the same semantic > >value, i.e. all with the last string ($4). > > This is one of the most frequently asked question on this list: You > forget to make copies of the strings in your lexer. Thus you only get > a pointer into a buffer, as you work with pointers. OK, I see. That's solved my problem. > > >PS. I have to use bison 1.24 so you may not be able to help me. > > This is rather old; the latest release is 2.0 Yes, I know, but I prefer to wait for a C++ output for bison, as it says in the FAQ section of the manual. Thank you very much, E. SR ___ Help-bison@gnu.org http://lists.gnu.org/mailman/listinfo/help-bison
Re: Problem with a simple grammar
At 15:35 +0200 2005/04/17, Eulogio Serradilla wrote: > This is rather old; the latest release is 2.0 Yes, I know, but I prefer to wait for a C++ output for bison, as it says in the FAQ section of the manual. Bison already has some C++ support, though you might not get the file setup you may want. But if you are starting afresh, that might not be a problem to you. -- Hans Aberg ___ Help-bison@gnu.org http://lists.gnu.org/mailman/listinfo/help-bison
Re: Problem with a simple grammar
> At 15:35 +0200 2005/04/17, Eulogio Serradilla wrote: > > > This is rather old; the latest release is 2.0 > > > >Yes, I know, but I prefer to wait for a C++ output for bison, as it says > > in the FAQ section of the manual. > > Bison already has some C++ support, though you might not get the file > setup you may want. But if you are starting afresh, that might not be > a problem to you. Actually, I'm using bison++ based on bison 1.19 and it works very well. When there is some documentation in bison about a C++ parser I will change my code. E. SR ___ Help-bison@gnu.org http://lists.gnu.org/mailman/listinfo/help-bison
Re: Problem with a simple grammar
At 19:44 +0200 2005/04/17, Eulogio Serradilla wrote: Actually, I'm using bison++ based on bison 1.19 and it works very well. When there is some documentation in bison about a C++ parser I will change my code. Bison++ is a program different from Bison, supposedly old. Bison has a C++ test, that is executed if you do a "make check". (I am using Bison 2.0 with a special tweak for my own C++ skeleton file, so that can't be used straight off.) -- Hans Aberg ___ Help-bison@gnu.org http://lists.gnu.org/mailman/listinfo/help-bison
Re: Problem with a simple grammar
> At 19:44 +0200 2005/04/17, Eulogio Serradilla wrote: > >Actually, I'm using bison++ based on bison 1.19 and it works very well. > > When there is some documentation in bison about a C++ parser I will > > change my code. > > Bison++ is a program different from Bison, supposedly old. Bison has > a C++ test, that is executed if you do a "make check". (I am using > Bison 2.0 with a special tweak for my own C++ skeleton file, so that > can't be used straight off.) I may give it a try, thank you for your help. E. SR. ___ Help-bison@gnu.org http://lists.gnu.org/mailman/listinfo/help-bison
