YACC Rules not reduced - yacc

Question

This is my code calc.y. I keep getting the error:
yacc: 1 rule never reduced
yacc: 3 reduce/reduce conflicts
not really sure what this means
Ive done some research in other places but I am now lost. Im guessing the rules being referred to is program and statement but even so... what does the reduce rule mean?
%{
#include <stdio.h>
FILE *outfile;
int yyline = 1;
int yycolumn = 1;
%}
%union{
int nw;
struct{
int v;
char s[1000];
}attr;
}
%token SEMInumber
%token LPARENnumber
%token <nw> ICONSTnumber
%token BEGINnumber
%token PROGRAMnumber
%token MINUSnumber
%token TIMESnumber
%token <nw> VARnumber
%token INTnumber
%token EOFnumber
%token COMMAnumber
%token RPARENnumber
%token <nw>IDnumber
%token ENDnumber
%token ISnumber
%token PLUSnumber
%token DIVnumber
%token PRINTnumber
%token EQnumber
%type <attr> exp
%type <attr> term
%type <attr> factor
%%
program: PROGRAMnumber IDnumber ISnumber compstate
;
compstate: BEGINnumber {print_header();} statement ENDnumber{print_end();}
| BEGINnumber {print_header();} statement SEMInumber statement ENDnumber{print_end();}
;
statement: IDnumber EQnumber exp
| PRINTnumber exp
| declaration
;
declaration: VARnumber IDnumber
| VARnumber IDnumber COMMAnumber IDnumber
;
exp: term {$$.v = $1.v; strcpy($$.s, $1.s);}
| exp PLUSnumber term {$$.v = $1.v + $3.v; sprintf($$.s, "(%s) + (%s)", $1. s, $3.s);}
| exp MINUSnumber term {$$.v = $1.v - $3.v; sprintf($$.s, "(%s) - (%s)", $1. s, $3.s);}
;
term: factor {$$.v = $1.v; strcpy($$.s, $1.s);}
| term TIMESnumber factor {$$.v = $1.v * $3.v; sprintf($$.s, "(%s) * (%s)", $1.s, $3.s);}
| term DIVnumber factor {$$.v = $1.v / $3.v; sprintf($$.s, "(%s) / (%s)", $1.s, $3.s);}
;
factor: ICONSTnumber {$$.v = $1; sprintf($$.s, "%d", $1);}
| IDnumber {$$.v = $1.v; strcpy($$.s, $1.s);}
| LPARENnumber exp RPARENnumber {$$.v = $2.v; strcpy($$.s, $2.s);}
;
%%
int main()
{
if(!yyparse())
{
printf("accept\n");
}
else
printf("reject\n");
}
void print_header() {}
void print_end(){}
void yyerror(const char *str)
{
printf("yyerror: %s at line %d\n", str, yyline);
}

Answer 1

When compstate shifts the BEGINnumber token, two inner rules for the mid rule action {print_header();} can be both reduced resulting in a R/R conflict. Youe can replace
compstate: BEGINnumber {print_header();} statement ENDnumber{print_end();}
| BEGINnumber {print_header();} statement SEMInumber statement
ENDnumber{print_end();}
;
with, for example
begin_number:
BEGINnumber { print_header(); }
compstate: begin_number statement ENDnumber{print_end();}
| begin_number statement SEMInumber statement
ENDnumber{print_end();}
;
to solve the conflict.

Answer 2

Informative Messages
%s: %d rules never reduced
Some rules are never used, either because they weren't used in the grammar or because they
were on the losing end of shift/reduce or reduce/reduce conflicts. Either change the
grammar to use the rules or remove them.