about recursive functions

[ft95]

Hi,I had a questin about recursive functions.

// string_reverse.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream> 
using namespace std;

void sting_reverse(char [],int,int);

int _tmain(int argc, _TCHAR* argv[])
{
	const int size=20;
	char statement[size];
	int x,i=0;
	x=size;

	cout<<"Enter the statement:";
	cin.getline(statement,size,'\n');
	x=strlen(statement);
	sting_reverse(statement, x,i);
	return 0;
}

void sting_reverse(char reverse_str [],int size,int i)
{
	
	if(i==size)
	return;
	 sting_reverse(reverse_str,size,i+1);
		cout<<reverse_str[i];

	
}

// string_reverse.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <iostream> 
using namespace std;

void sting_reverse(char [],int,int);

int _tmain(int argc, _TCHAR* argv[])
{
	const int size=20;
	char statement[size];
	int x,i=0;
	x=size;

	cout<<"Enter the statement:";
	cin.getline(statement,size,'\n');
	x=strlen(statement);
	sting_reverse(statement, x,i);
	return 0;
}

void sting_reverse(char reverse_str [],int size,int i)
{
	
	if(i==size)
	return;
	 return sting_reverse(reverse_str,size,i+1);
		cout<<reverse_str[i];

	
}

what is difference between these two function?
In other word,when should use "return" in second function call?

[vlad from moscow]

In fact these two functions are equivalent. There is no need to specify the second return in the last function.

[ft95]

So there isn't any diffrence between these two codes.Is there?
how about other recursive functions?
for example fibonacci or factorial?

[MiiNiPaa]

It's a void function. You don't need to use return at all. In your first example return used to end function prematurely. Your second example actually will never execute cout<<reverse_str[i]; routine, so it won't work at all.

[ft95]

will never execute cout<<reverse_str[i];

why?

[vlad from moscow]

You exit the function with the return statement

return sting_reverse(reverse_str,size,i+1);


So the next statement will not be executed.

cout<<reverse_str[i];

[vlad from moscow]

You could write


return ( void ) ( sting_reverse(reverse_str,size,i+1),
cout<<reverse_str[i] );

[ft95]

You could write


return void ( sting_reverse(reverse_str,size,i+1),
cout<<reverse_str[i] );

What is difference between this code and my code???!!!
They are similar to each other.Aren't they?

[vlad from moscow]

I made in my code snip a typo that I updated already. Should be either

return ( void ) ( sting_reverse(reverse_str,size,i+1), cout<<reverse_str[i] );

or

return void ( ( sting_reverse(reverse_str,size,i+1), cout<<reverse_str[i] ) );

The difference between my code and your code is that I have one return statement while you have two statements: the first one is the return statement and the second one is the expression statement. The expression statement will not be executed because the control exits the function.

[ft95]

I think that understood... .

thank you ...

[vlad from moscow]

You could write the function simpler

void string_reverse( const char *s )
{
	if ( *s ) return ( void( ( string_reverse( s + 1 ), std::cout << *s ) ) );
}

or as

void string_reverse( const char *s )
{
	if ( *s ) string_reverse( s + 1 ), std::cout << *s;
}