C ++帮助中的解析器！！我有流程图 [英] Parser in C++ Help!! I Have a Flowchart

问题描述

推荐答案

另一个版本

 

/***************************************************
 The following program will take user's input
 and check whether it is in the following language:

 <S> ---> a <B> | <A> | b
 <A> ---> c <A> | c
 <B> ---> d | <A>
****************************************************/


#include<iostream>
#include<string>
using namespace std;
#include<stdlib.h> // for the exit(1) function


char text[200];   // for input storage
char ThisOne;    // for the checking character 


char SProd(char ThisOne ); // <S> --> a <B> | <A> | b
char AProd(char ThisOne);  // Grammar 
char XProd(char ThisOne, char x);
char BProd(char ThisOne ); // <B> --> d   | <A>



int main()
{
		 cout<<"Enter a string"<<endl;
		 cin>>text;
		 ThisOne = lexical();
		 SProd();
		 if(ThisOne == '\0')
		  cout<<"valid"<<endl;
		 else
		 cout<<"Invalid"<<endl; 
}


char XProd(char ThisOne, char x)
{
		ThisOne = XProd(ThisOne, 'a');
		ThisOne	 = XProd(ThisOne, 'b');
		ThisOne  = XProd(ThisOne, 'c');
		ThisOne	 = XProd(ThisOne, 'd');
		return ThisOne;
}


char SProd(char ThisOne )
{
	if(ThisOne == 'b')
	{
		ThisOne++;
	}
	else{
		if(ThisOne == 'a')
		{
			ThisOne++;
			BProd(ThisOne);
		}
		else{
			AProd( ThisOne);
		}
	}


char AProd(char ThisOne)
{
 if(ThisOne != 'c' )
 {
	cout<<"Invalid"; 
	exit(1);
 }
 else{
	 ThisOne++; 

 
 while(ThisOne == 'c')
	 ThisOne++
	 return ThisOne
 }
}

  
char BProd(char ThisOne )
{
	if(ThisOne == 'd')
		This++;
		return ThisOne;
	else
		AProd(char ThisOne, char y);
}

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