a.c

词法分析的原程序啊

 #include <stdio.h> 
#include <string.h> 
#include <process.h> 
#define MAX 50
 void main() 
 { FILE *in,*out;/*存放输入字符串和输出单词串的文件*/ 
   char arr[MAX];/*arr数组存放单词符号*/ 
   char currentchar;/*currentchar存放当前输入字符*/ 
   int i=0;/*arr数组的一个指针*/ 
   /*以读方式打开输入文件*/ 
   if((in=fopen("infile.txt","r"))==NULL) 
   {printf("cannont open infile\n"); exit(0); } 
   /*以写方式打开输出文件*/ 
   if((out=fopen("outfile.txt","w"))==NULL) 
   {printf("cannout open outfile\n"); exit(1); } 
   /*过滤掉开始的空格*/ 
   currentchar=fgetc(in); 
   while(currentchar==' ') 
   currentchar=fgetc(in); 
   /*判断常数部分*/ 
   if(currentchar>='0'&&currentchar<='9') 
   { arr[i++]=currentchar; currentchar=fgetc(in);
   /*再读入下一个字符*/ 
      while(currentchar>='0'&&currentchar<='9') 
	  { arr[i++]=currentchar; currentchar=fgetc(in); } 
     if(currentchar!='.')/*如果当前读入的符号不为小数点，则常数读完毕，输出此常数*/ 
		{ fprintf(out,"%s,%6d,%s\n","常数",2,arr);/*格式化输出到目标文件， 2代表类别
            arr为内码值，规定用数字本身代表*/ }
     else/*当前字符为小数点则继续向下读入*/ 
	 { arr[i++]=currentchar; currentchar=fgetc(in); 
	   while(currentchar>='0'&&currentchar<='9') 
	   { arr[i++]=currentchar; currentchar=fgetc(in); } 
	   fprintf(out,"%s,%6d,%s\n","常数",2,arr); 
	 }
   } /*判断标识符和关键字部分*/ 
   else if(currentchar>='a'&&currentchar<='z')
	   { i=0;/*清空arr字符数组*/
         while((currentchar>='a'&&currentchar<='z')||(currentchar>='0'&&currentchar<='9')) 
		 { arr[i++]=currentchar; currentchar=fgetc(in); } /*把字符数组arr和关键字表比较，判断单词串是关键字还是标识符*/ arr[i++]='\0'; /*关键字的类别编码从3开始个不一样，所以没必要再用内码值标识*/ if(strcmp(arr,"program")==0) fprintf(out,"%s,%6d\n",arr,3); else if(strcmp(arr,"begin")==0) fprintf(out,"%s,%6d\n",arr,4); else if(strcmp(arr,"end")==0) fprintf(out,"%s,%6d\n",arr,5); else if(strcmp(arr,"if")==0) fprintf(out,"%s,%6d\n",arr,6); else if(strcmp(arr,"then")==0) fprintf(out,"%s,%6d\n",arr,7); else if(strcmp(arr,"else")==0) fprintf(out,"%s,%6d\n",arr,8); else fprintf(out,"s%,%6d,%s\n","标识符",1,arr);/*标识符的类别编码为1， 内码值用字符串本身表*/
		} else if(currentchar=='+') 
			 { fprintf(out,"%c,%6d\n",currentchar,9); 
		       currentchar=fgetc(in); } 
		       else if(currentchar=='-') 
				   { fprintf(out,"%c,%6d\n",currentchar,10);
			         currentchar=fgetc(in); }
			        else if(currentchar=='*') 
						{ fprintf(out,"%c,%6d\n",currentchar,11); 
					      currentchar=fgetc(in); } 
					     else if(currentchar=='/') 
							 { fprintf(out,"%c,%6d\n",currentchar,12); 
						       currentchar=fgetc(in); } 
						       else if(currentchar==';') 
									{ fprintf(out,"%c,%6d\n",currentchar,13); 
							          currentchar=fgetc(in); }
							          else  if(currentchar==':') 
										   {  i=0; arr[i++]=currentchar; 
									         currentchar=fgetc(in); 
											   if(currentchar=='=') 
											   { arr[i++]=currentchar; 
											    fprintf(out,"%s,%6d\n",arr,14); }
										     	else
												fprintf(out,"%s,%6d\n",arr,15);} 
									          else if(currentchar=='=') 
												  { i=0; arr[i++]=currentchar;
											        currentchar=fgetc(in);
													if(currentchar=='=') 
													{ arr[i++]=currentchar; 
													fprintf(out,"%s,%6d\n",arr,16); } 
													else 
														fprintf(out,"%s,%6d\n",arr,17); }
											  else if(currentchar=='>') 
											  { i=0; arr[i++]=currentchar;
											  currentchar=fgetc(in); 
											            if(currentchar=='=') 
														{ arr[i++]=currentchar; 
											              fprintf(out,"%s,%6d\n",arr,18); } 
											            else fprintf(out,"%s,%6d\n",arr,19); } 
											         else if(currentchar=='<') 
													 { i=0; arr[i++]=currentchar; 
													   currentchar=fgetc(in);
													      if(currentchar=='=') 
														  { arr[i++]=currentchar; 
														   fprintf(out,"%s,%6d\n",arr,20); }
														  else if(currentchar=='>') 
														  {    arr[i++]=currentchar; 
														       fprintf(out,"%s,%6d\n",arr,21); } 
														     else fprintf(out,"%s,%6d\n",arr,22); } 
													     else if(currentchar=='#') exit(2);
														      else printf("the %c is not a correct letter\n",currentchar); 
															  fclose(in);
															  fclose(out); 
 }