expr.lex

来自「flex」· LEX 代码 · 共 36 行

/*
 * expr.lex : Scanner for a simple
 *            expression parser.
 */

%{
#include "y.tab.h"

%}

%%

[0-9]+     { yylval.val = atol(yytext);
             return(NUMBER);
           }
[0-9]+\.[0-9]+ { 
             sscanf(yytext,"%f",&yylval.val);
             return(NUMBER);
           }
"+"        return(PLUS);
"-"        return(MINUS);
"*"        return(MULT);
"/"        return(DIV);
"^"        return(EXPON);
"("        return(LB);
")"        return(RB);
\n         return(EOL);
[\t ]*     /* throw away whitespace */
.          { yyerror("Illegal character"); 
             return(EOL);
           }
%%