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%{
#define YYSTYPE double /* data type of yacc stack */
#include <stdio.h>
#include <ctype.h>
#include <math.h>
int yylex();
int yyerror(const char * s);
%}
%token NUMBER
%left '+' '-' /* left associative, same precedence */
%left '*' '/' '%' /* left assoc., higher precedence */
%left UNARYMINUS
%%
list: /* nothing */
| list '\n'
| list expr '\n' { printf("%lf\n", $2); }
;
expr: NUMBER { $$ = $1; }
| expr '+' expr { $$ = $1 + $3; }
| expr '-' expr { $$ = $1 - $3; }
| expr '*' expr { $$ = $1 * $3; }
| expr '/' expr { $$ = $1 / $3; }
| expr '%' expr { $$ = fmod($1, $3); }
| '-' expr %prec UNARYMINUS { $$ = -$2; }
| '(' expr ')' { $$ = $2; }
;
%%
int lineno = 1;
int main(int argc, char** argv)
{
yyparse();
return 0;
}
int yylex()
{
int c;
do {
c = getchar();
} while (c == ' ' || c == '\t');
if (c == EOF)
return 0;
if (c == '.' || isdigit(c)) {
ungetc(c, stdin);
scanf("%lf", &yylval);
return NUMBER;
}
if (c == '\n')
lineno++;
return c;
}
int yyerror(const char* s)
{
fprintf(stderr, "Error occured near line %d\n", lineno);
return 0;
}
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