lexer.l

来自「学习lemon语法分析的windows程序」· L 代码 · 共 64 行

%{
#include "lexglobal.h" 
#include "example5.h"
#include <string.h>
#include <math.h>

int line = 1, col = 1;


%}

%%


[0-9]+|[0-9]*\.[0-9]+    {                      col += (int) strlen(yytext); 
                                                yylval.dval = atof(yytext); 
                                                return NUM; }
[ \t]   { col += (int) strlen(yytext); }               /* ignore but count white space */
[A-Za-z][A-Za-z0-9]*                           { /* ignore but needed for variables */

                                                return 0;
                                               }

"+"           {  return PLUS; }
"-"           {  return MINUS; }
"*"           {  return TIMES; }
"/"           {  return DIVIDE; }



\n      { col = 0; ++line; return NEWLINE; }

.       { col += (int) strlen(yytext); return yytext[0]; }
%%
/**
 * reset the line and column count
 *
 *
 */
void reset_lexer(void)
{

  line = 1;
  col  = 1;

}

/**
 * yyerror() is invoked when the lexer or the parser encounter
 * an error. The error message is passed via *s
 *
 *
 */
void yyerror(char *s)
{
  printf("error: %s at line: %d col: %d\n",s,line,col);

}

int yywrap(void)
{
  return 1;
}