逆波蘭記號計算器【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 (); }

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

?

中輟符號計算器【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 (); }

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

?

轉載于:https://www.cnblogs.com/xiaozong/p/6289807.html

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