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: '\n'| exp '\n' { printf ("\t%.10g\n", $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' { $$ = -$1; }
;
%%#include <ctype.h>int yylex (void) {int c;/* Skip white space. */while ((c = getchar ()) == ' ' || c == '\t') ;/* Process numbers. */if (c == '.' || isdigit (c)) {ungetc (c, stdin);scanf ("%lf", &yylval);return NUM;}/* Return end-of-input. */if (c == EOF) return 0;/* Return a single char. */return c;
}void yyerror (char const *s) {fprintf (stderr, "%s\n", s);
}int main (void) {return yyparse ();
}
------------------运行----------------------
bison rpcalc.y
gcc -o rpcalc -lm rpcalc.tab.c
./rpcalc
4 9 +
13
中辍符号计算器【文件名calc.y】
%{
#define YYSTYPE double
#include <math.h>
#include <stdio.h>
int yylex (void);
void yyerror (char const *);
%}
/* Bison declarations. */
%token NUM
%left '-' '+'
%left '*' '/'
%right '^' /* exponentiation */
%% /* The grammar follows. */
input:| input line
;
line:'\n'
| exp '\n' { printf ("\t%.10g\n", $1); }
;
exp:NUM { $$ = $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 == '\t') ;/* 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\n", s);
}int main (void) {return yyparse ();
}
------------------运行----------------------
bison calc.y
gcc -o calc -lm calc.tab.c
./calc
8*(1+3)
32
