a1.cpp

语法分析

#include <stdio.h>
#include <string.h>
#include <ctype.h>
#include <malloc.h>
#include <conio.h>
#include <iostream>
using namespace std;



//#define NULL 0
/*
struct buf
{
  char kind;
  char value;
}

buf bb[100];

*/
string  Box[200];
char ch;
char *keyword[8]={"do","begin","else","end","if","then","var","while"};
char *operatornum[4]={"+","-","*","/"};
char *comparison[6]={"<","<=","=",">",">=","<>"};
char *interpunction[6]={",",";",":=",".","(",")"};

bool search(char searchstr[],int wordtype)
{
 int i;
 switch (wordtype)
 {
 case 1:for(i=0;i<=7;i++)
     {
      if(strcmp(keyword[i],searchstr)==0)
       return(true);
      
     }
 case 2:{
  for(i=0;i<=3;i++)
  {
   if(strcmp(operatornum[i],searchstr)==0)
    return(true);
  }
  break;
     }
 case 3: for(i=0;i<=5;i++)
   {
    if(strcmp(comparison[i],searchstr)==0)
     return(true);
   }
 case 4: for(i=0;i<=5;i++)
   {
    if(strcmp(interpunction[i],searchstr)==0)
     return(true);
   }
  
 
 }
 return(false);
}

char letterprocess (char ch)//字母处理函数
{
if (isalpha(ch)!=0)
{


				 int i=-1;
				 char letter[20];
				 while (isalnum(ch)!=0)
				 {
				  letter[++i]=ch;
 
				  ch=getchar();
				 } 
				 letter[i+1]='\0';
				 if (search(letter,1))
				 {
				  cout<<"("<<letter<<",~~  )"<<endl;
				 }
				 else
				 {
				  cout<<"( indentifier,"<<letter<<"  )"<<endl;
				 }


}
/* return(ch);
}

char numberprocess(char ch)//数字处理程序
{*/
 /*int*/
else
{
	if (isdigit(ch)!=0)

	{
			int	i=-1;
				 char num[20];
				 while (isdigit(ch)!=0)
				 {
				  num[++i]=ch;
				  ch=getchar();
				 }
				 if(isalpha(ch)!=0)
				 {
				  while(isspace(ch)==0)
				  {
				   num[++i]=ch;
  
				   ch=getchar();
				  }
				  num[i+1]='\0';
				  cout<<"错误！非法标识符: " <<num<<endl;
				  goto A;
				 }
				 num[i+1]='\0';
   
				 cout<<" ( digit,"<<num<<" )"<<endl;
  
				A: cout<< "  "<<endl;


	}
/*  return(ch);
}

char otherprocess(char ch)
{*/
 /*int*/
		else
		{


		int	 i=-1;
			 char other[20];
			 if (isspace(ch)!=0)
			 {
 
				 ch=getchar();
			  goto B;
			 }
			 while ((isspace(ch)==0)&&(isalnum(ch)==0))
			 {
			  other[++i]=ch;
              ch=getchar();
			 }
			 other[i+1]='\0';
				 if (search(other,2))
				  cout<<"("<<other<<",~~ ) "<<endl;
				 else
				  if (search(other,3))
					cout<<"("<<other<<" , ~~ )"<<endl;
				  else
				   if (search(other,4))
					cout<<"("<<other<<" , ~~ )"<<endl;
				   else 
			   //printf("错误！非法字符：%s\n",other);
			   cout<<"   错误_____非法字符： "<<other<<endl;
			B: return (ch);

		}

}
}










void main()
{
S:
  cout<<"***************************词法分析器*********************************"<<endl<<"******  输入源程序："<<endl;
 char str;

 str=getchar();
  while( str!='#')
  {
   /*if (isalpha(str)!=0)
       str=letterprocess(str);
   else
   {
		if (isdigit(str)!=0)
		    str=numberprocess(str);
		else
		     str=otherprocess(str);
   }*/

   letterprocess(str);

  }
  cout<<"是否继续下一个词法分析[ y/ ~~]：";
  char ch;
  cin>>ch;
  if(ch=='y')
	  goto S;
}