bison实例

逆波兰记号计算器【文件名rpcalc.y】

%{
#define YYSTYPE double
#include <stdio.h>
#include <math.h>
#include <ctype.h>
int yylex (void);
void yyerror (char const *);
%}
 
%token NUM
 
%%
input:    /* empty */
     | input line
    ;
 
line:     '
'
    | exp '
'      { printf ("	%.10g
", $1); }
;
 
exp:      NUM           { $$ = $1;           }
   | exp exp '+'   { $$ = $1 + $2;      }
    | exp exp '-'   { $$ = $1 - $2;      }
    | exp exp '*'   { $$ = $1 * $2;      }
    | exp exp '/'   { $$ = $1 / $2;      }
     /* Exponentiation */
    | exp exp '^'   { $$ = pow($1, $2); }
    /* Unary minus    */
    | exp 'n'       { $$ = -$1;          }
;
%%
 
#include <ctype.h>
 
int yylex (void) {
       int c;
 
/* Skip white space.  */
       while ((c = getchar ()) == ' ' || c == '	') ;
 
/* Process numbers.  */
       if (c == '.' || isdigit (c)) {
       ungetc (c, stdin);
       scanf ("%lf", &yylval);
       return NUM;
     }
 
       /* Return end-of-input.  */
       if (c == EOF) return 0;
 
       /* Return a single char.  */
       return c;
}
 
void yyerror (char const *s) {
    fprintf (stderr, "%s
", s); 
}
 
int main (void) {
    return yyparse ();
}

------------------运行----------------------
bison rpcalc.y
gcc -o rpcalc -lm rpcalc.tab.c
./rpcalc
4 9 +
　　　　  13

中辍符号计算器【文件名calc.y】

%{
#define YYSTYPE double
#include <math.h>
#include <stdio.h>
int yylex (void);
void yyerror (char const *);
%}
/* Bison declarations.  */
%token NUM
%left '-' '+'
%left '*' '/'
%right '^'        /* exponentiation */
%% /* The grammar follows.  */
input:
  
| input line
;
line:
  '
'
| exp '
'  { printf ("	%.10g
", $1); }
;
exp:
  NUM                { $$ = $1;           }
| exp '+' exp        { $$ = $1 + $3;      }
| exp '-' exp        { $$ = $1 - $3;      }
| exp '*' exp        { $$ = $1 * $3;      }
| exp '/' exp        { $$ = $1 / $3;      }
| '-' exp               { $$ = -$2;          }
| exp '^' exp        { $$ = pow ($1, $3); }
| '(' exp ')'        { $$ = $2;           }
;
%%

#include <ctype.h>
 
int yylex (void) {
       int c;
 
/* Skip white space.  */
       while ((c = getchar ()) == ' ' || c == '	') ;
 
/* Process numbers.  */
       if (c == '.' || isdigit (c)) {
       ungetc (c, stdin);
       scanf ("%lf", &yylval);
       return NUM;
     }
 
       /* Return end-of-input.  */
       if (c == EOF) return 0;
 
       /* Return a single char.  */
       return c;
}
 
void yyerror (char const *s) {
    fprintf (stderr, "%s
", s); 
}
 
int main (void) {
    return yyparse ();
}

------------------运行----------------------
bison calc.y
gcc -o calc -lm calc.tab.c
./calc
8*(1+3)
　　　　  32