ref: 1e95b1cbb2a05e23ada69db3093b1a3d389c97f3
dir: /calc.y/
%{ #include <u.h> #include <libc.h> #include <bio.h> #include <ctype.h> int yylex(void); int yyparse(void); void yyerror(char*); Biobuf *bf; %} %union{ int i; } %token<i> NUM %type<i> expr %left '+' '-' %left '*' '/' '%' %% input: | input expr '\n' { print("%d\n", $2); } expr: NUM { $$ = $1; } | '(' expr ')' { $$ = $2; } | expr '+' expr { $$ = $1 + $3; } | expr '-' expr { $$ = $1 - $3; } | expr '*' expr { $$ = $1 * $3; } | expr '/' expr { $$ = $1 / $3; } | expr '%' expr { $$ = $1 % $3; } %% void yyerror(char *s) { fprint(2, "%s\n", s); } int getnum(int c) { char s[64], *p; for(p=s, *p++=c; isdigit(c=Bgetc(bf));) if(p < s+sizeof(s)-1) *p++ = c; *p = 0; Bungetc(bf); return strtol(s, nil, 10); } int yylex(void) { int n, c; do c = Bgetc(bf); while(c != '\n' && isspace(c)); if(isdigit(c)){ yylval.i = getnum(c); return NUM; }else if(c == 'd'){ n = getnum(Bgetc(bf)); yylval.i = nrand(n != 0 ? n : 1); return NUM; }else return c; } void main(int argc, char **argv) { ARGBEGIN{ }ARGEND if((bf = Bfdopen(0, OREAD)) == nil) sysfatal("Bfdopen: %r"); yyparse(); }