lexer.l.bak

构造C--语言的词法分析器。将一个C--语言程序分割成token串的序列。处理C--语言的所有token类型。

%{
#include <stdio.h>
#include <string.h>
#include <malloc.h>
#include <math.h>
#include <stdlib.h>

int nline = 1;

struct id_entry {
	char * id;
	struct id_entry *next; /* next entry on hash chain */
};

struct id_entry * id_hash_table[1024];

int hash(char * name) 
{
  int h = *name++;
  while (*name) h = h << 4 + *name++;
  return h;
}

char * insert_id(char *name)
{ int h = hash(name) & 1024;
  struct id_entry *p=id_hash_table[h];
  while (p && (strcmp(p->id, name) != 0)) p = p->next;
  if (p) return p->id;
  p = (struct id_entry *)malloc(sizeof *p);
  p->id = (char *)malloc(strlen(name)+1);
  strcpy(p->id, name);
  p->next = id_hash_table[h];
  id_hash_table[h] = p; /* 新名字在表头 */
  return p->id;
}  

%}

/*正规定义*/
delim      [ \t]
ws         {delim}+
leter      [A-Za-z]                                        
digit      [0-9]
id         {leter}({leter}|{digit})*  
number     {digit}+(\.{digit}+)?(E[+\-]?{digit}+)?          
comment    (\#[^\n]*)|(\/\*([^*]|\n|(\*+([^*/]|\n)))*\*+\/)
sentence   \"(.)*\"  
chartype   (\'([^\n]|\n)\')|\'\'
special    [\@\~\\\$\`] 
pun	   \(|\)|\{|\}|<=|>=|=|\+|\-|\;|\*|\,
%%
"\n"          { nline++;}
{comment}  {/*对预处理和注释部分没有动作和返回值*/}
{ws}       {/*对空白串没有动作和返回值*/}
{number}   { /*yylval._ident = insert_id(yytext);*/fprintf(yyout,"NUM %s\n",yytext);}
{sentence}  {fprintf(yyout,"STRING %s\n",yytext);}
{chartype}  {fprintf(yyout,"CONST_CHAR %s\n",yytext);}
"__stdcall" {fprintf(yyout,"STDCALL %s\n",yytext);}
"__cdecl"   {fprintf(yyout,"CDECL %s\n",yytext);}
"if"   {fprintf(yyout,"KEYWORD %s\n",yytext);}
"int"   {fprintf(yyout,"KEYWORD %s\n",yytext);}
"void"   {fprintf(yyout,"KEYWORD %s\n",yytext);}
"char"   {fprintf(yyout,"KEYWORD %s\n",yytext);}
"else"   {fprintf(yyout,"KEYWORD %s\n",yytext);}
"while"   {fprintf(yyout,"KEYWORD %s\n",yytext);}
"return"   {fprintf(yyout,"KEYWORD %s\n",yytext);}
{pun}	   {fprintf(yyout,"PUN %s\n",yytext);}
{id}       { /*yylval._ident = insert_id(yytext); */fprintf(yyout,"ID %s\n",yytext);}


.  { /*return yytext[0];*/ }       
%%

error(char *m)
{
     fprintf(stderr,"%s\n",m);
     exit(1);         /*非正常终止*/
}

int main(int argc,char *argv[]){
   if(argc==1){
		information(); //当命令行不带参数时,输出提示信息
	}
	else{
   if(argc==3){
      if((yyin=fopen(argv[1],"r"))==NULL){
 	       printf("can't open %s\n",argv[1]);
	       exit(0);
	       }
	    if((yyout=fopen(argv[2],"w"))==NULL){
	       printf("can't open %s\n",argv[2]);
	       exit(0);
	       }
      
   
  yylex();
  return 0; 
   }
  else
     printf("Common Error!\n");
   }
   
}

int yywrap(){return 1;}