Update lexer.l

Author: KatameRonin

lexer.l

@@ -8,12 +8,7 @@ int idx =0 ;
 
 [a-z]+ {c[idx++]='i';}
 [0-9]+ {c[idx++]='n';}
-"(" {c[idx++]='(';}
-")" {c[idx++]=')';}
-"+" {c[idx++]='+';}
-"-" {c[idx++]='-';}
-"*" {c[idx++]='*';}
-"/" {c[idx++]='/';}
+[(,),+,-,*,/] {c[idx++]=*yytext;}
 
 %%
 void yyerror(char *s) {