2.c

一、实验目的：编制一个源程序的输入过程

/*一个简单的词法分析程序：  */ 
    
    /*其中包括两个文件   compiler.c   和   search.h   ，把search.h放到include   文件夹里就行。*/   
    
  /********************compiler.c*************************************/   
    
  #include<stdio.h>   
  #include<string.h>   
  #include<ctype.h>   
  #include"search.h"   
  extern   int   reserve(char*);   
  extern   void   output(int,char*);   
  char   token[20];   
  char   ch;   
  int   i,c;   
    
  void   scanner(FILE   *fp)   
  {   
    ch=fgetc(fp);   
    if(isalpha(ch))   
    {   
      token[0]=ch;   
      i=1;   
      ch=fgetc(fp);   
      while(isalpha(ch)||isalnum(ch))   
      {   
        token[i]=ch;   
        i++;   
        ch=fgetc(fp);   
      }   
      fseek(fp,-1,1);   
      token[i]='\0';   
      c=reserve(token);   
      if(c!=-1)   
                  output(c,token);   
      else   
                  output(10,token);   
    }   
    else   if(isdigit(ch))   
              {   
      token[0]=ch;   
      ch=fgetc(fp);   
      i=1;   
      while(isdigit(ch))   
      {   
        token[i]=ch;   
        i++;   
        ch=fgetc(fp);   
      }   
      token[i]='\0';   
      fseek(fp,-1,1);   
      output(11,token);   
              }   
    else   
      switch(ch)   
      {   
        case'=':ch=fgetc(fp);   
          if(ch=='=')   
            output(39,"==");   
          else   
          {   
          fseek(fp,-1,1);   
          output(21,"=");   
          }   
          break;   
        case'+':output(22,"+");break;   
        case'-':output(23,"-");break;   
        case'*':output(24,"*");break;   
        case'/':output(25,"/");break;   
        case'(':output(26,"(");break;   
        case')':output(27,")");break;   
        case'[':output(28,"[");break;   
        case']':output(29,"]");break;   
        case'{':output(30,"{");break;   
        case'}':output(31,"}");break;   
        case',':output(32,",");break;   
        case':':output(33,":");break;   
        case';':output(34,";");break;   
        case'>':ch=fgetc(fp);   
          if(ch=='=')   
            output(37,">=");   
          else   
          {   
          fseek(fp,-1,1);   
          output(35,">");   
          }   
          break;   
        case'<':ch=fgetc(fp);   
          if(ch=='=')   
            output(38,"<=");   
          else   
          {   
          fseek(fp,-1,1);   
          output(36,"<");   
          }   
          break;   
        case'!':ch=fgetc(fp);   
          if(ch=='=')   
            output(40,"!=");   
          else   
          {   
          fseek(fp,-1,1);   
          output(-1,"ERROR!");   
          }   
          break;   
      }   
    
  }   
  void   main()   
  {               FILE   *fp;   
    char   wenjian[30];   
    printf("Please   input   the   file   you   want   to   transform:");   
    scanf("%s",&wenjian);   
    fp=fopen(wenjian,"r");   
    while(!feof(fp))   
    {   
      scanner(fp);   
    }   
  }   
    
  /**************************search.h*********************************/   
    
  extern   struct   table   
  {   
      int   id;   
      char   code[10];   
  };   
  struct   table   key[31]   =   {{1,"main"},{2,"int"},{3,"char"},{4,"if"},{5,"else"},{6,"for"},{7,"while"},{10,"ID"},{20,"NUM"},{-1,"ERROR"}};   
  int   reserve(char*   p)   
  {     int   i=0;   
      for(i=0;i<9;i++)   
      {   
          if(strcmp(p,key[i].code)==0)   
          return(key[i].id);   
      }   
      return(-1);   
  }   
  void   output(int   t,char   *s)   
  {   
      printf("[   %-2d   ,   %-6s   ]\n",t,s);   
  }   
    
  /*******************************************************************/