chifa.txt

编译原理实现词法分析功能的试验源代码主要是输入一段程序输出单词系列

#include <iostream>
#include <stdio.h>
#include <string>
using namespace std;
void main()
{
char *keywords[]={"begin","call","const","do","end","if","odd","procedure","read","then","var","while","write"}; 
char *wsym[ ]={"beginsym" ,"callsym","constsym","dosym","endsym","ifsym","oddsym","proceduresym","readsym","thensym","varsym","whilesym" ,"writesym"};
	char *sym;
	int flag;
	int num;
	int cc;
	int k,i,j;
	char ch;
	char words[50];
	char id[50];
	cout<<"请输入一段程序:"<<endl;
	ch = getchar ();
	while (ch !='#')
	{
		if( ch<='z' && ch >='a' || ch<='Z' && ch>='A' )
		{
			k=0;
		do
		{
			if( k<49 )
			{
				words[k] = ch ;
				k++ ;
			}
			ch = getchar ();
		}while( ch<='z' && ch >='a' || ch<='Z' && ch>='A'|| ch<='9' && ch>='0' ) ;
		words[k] = '\0' ;
		strcpy( id, words ) ;
		i = 0;
		flag = 13;
		j = flag -1;
		do
		{
			k=(i+j)/2 ;
			cc=strcmp(id, keywords[k]);
			if( cc<0 ) 
			{
				j=k-1 ;
			}
			else if( cc>0 ) 
			{
				i=k+1 ;
			}
			else break ;
		}while( i<=j) ;
		if( i<=j )
		{
			sym=wsym[k] ;
			cout<<"("<<id<<","<<sym<<")"<<endl;
		}
		else
		{
			sym="ident" ;	 
			cout<<"("<<sym<<","<<id<<")"<<endl;
		}
		}
		else if( ch<='9' && ch>='0' )
		{
			num=0; 
			sym="number"; 
			do{
				num=10 * num + ch - '0' ;
				ch = getchar (); 
				}while( ch<='9' && ch>='0' ) ;
			cout<<"("<<"number"<<","<<num<<")"<<endl;
		}
		else if (ch ==' ')
		{
			ch = getchar();
		}
		else if (ch =='+')
		{	sym = "plus";
			cout<<"("<<sym<<","<<" "<<")"<<endl;
			ch = getchar (); 
		}
		else if (ch =='-')
		{	sym = "minus";
			cout<<"("<<sym<<","<<" "<<")"<<endl;
			ch = getchar (); 
		}
			else if (ch =='*')
		{	sym = "times";
			cout<<"("<<sym<<","<<" "<<")"<<endl;
			ch = getchar (); 
		}
			else if (ch =='-')
		{	sym = "slash";
			cout<<"("<<sym<<","<<" "<<")"<<endl;
			ch = getchar (); 
		}
			else if (ch =='=')
		{	sym = "equal";
			cout<<"("<<sym<<","<<" "<<")"<<endl;
			ch = getchar (); 
		}
			else if(ch==',')
		{
				sym="douhao";
				cout<<"("<<sym<<","<<" "<<")"<<endl;
			    ch = getchar (); 
		}
			else if(ch==';')
		{
				sym="fenhao";
				cout<<"("<<sym<<","<<" "<<")"<<endl;
			    ch = getchar (); 
		}
			else if(ch=='(')
		{
				sym="lparen";
				cout<<"("<<sym<<","<<" "<<")"<<endl;
			    ch = getchar (); 
		}
			else if(ch=='}')
		{
				sym="rparen";
				cout<<"("<<sym<<","<<" "<<")"<<endl;
			    ch = getchar (); 
		}
			else if(ch=='{')
		{
				sym="ldakuohao";
				cout<<"("<<sym<<","<<" "<<")"<<endl;
			    ch = getchar (); 
		}
			else if(ch=='}')
		{
				sym="rdakuohao";
				cout<<"("<<sym<<","<<" "<<")"<<endl;
			    ch = getchar (); 
		}
	
   }
	
}