I'm having some problems with operator management increase and decrease (prefixes and postfixes) using Flex / Bison, below is another answer :
How to fix YACC shift/reduce conflicts from post-increment operator?
I have read that the best solution seems to be to declare them as %nonassoc or in some cases use %right, I'm a little confused:
inserting these parameters I expect these results :
1 + ++1 ; // 3
1 + 1++ ; // 2
1 + --1 ; // 1
1 + 1-- ; // 2
however I receive this as an output :
1-3
2-3
2-3
2-3
I'll post the source I use :
...
%right tplus tmin
%nonassoc tINC tDEC
...
%type<integer> expr program
%%
program: expr tPV {printf ( "1-%d\n",$$); }
| program expr tPV {printf ( "2-%d\n",$$); }
;
expr: tINTEGER { $$ = $1; }
| expr tPLUS expr { $$ = $1 + $3; }
| expr tMIN expr { $$ = $1 - $3; }
| expr tMUL expr { $$ = $1 * $3; }
| expr tDIV expr { $$ = $1 / $3; }
| expr tMOD expr { $$ = $1 % $3; }
| tPLUS expr %prec tplus { $$ = $2; }
| tMIN expr %prec tmin { $$ = -$2; }
| tINC expr { $$ = ++$2; }
| expr tINC { $$ = $1++; }
| tDEC expr { $$ = --$2; }
| expr tDEC { $$ = $1--; }
| tP0 expr tP1 { $$ = $2; }
;
%%
can you give me some suggestions? Thanks in advance Claudio
Solution :
program: line
| program line
;
line: tPV { }
| expr tPV { printf("\n[%d]\n", $1); }
;
the error was not in grammar, but in non-terminal !
output :
main.exe < prova.txt
[3]
[2]
[1]
[2]
