reverse string help

[4ET0pfjN]

hi, it's not compiling for my function:

string r_reverse(string originalString, int index)
{
	
	if ( index < 0 )
		return originalString.at(0);
	else
		return originalString.at(index) + r_reverse(originalString, index - 1 );
}

[Vlykarye]

at() returns a char type, not a string type.

[4ET0pfjN]

also, while we're at it, how would i make the same function but it returns a pointer by taking in a string array?

[Vlykarye]

Depends on how you are using the function. I look at it, and I don't see it reversing anything... So I'm not really sure what the function should be doing.

But, if you want it to return a pointer, then just make it return a pointer.

string * r_reverse(string originalString, int index)
{	
	if ( index < 0 )
		return originalString.at(0);
	else
		return originalString.at(index) + r_reverse(originalString, index - 1 );
}

Now it returns a pointer to a string. HOWEVER, at() returns a character, so you should be getting a conversion error.

[4ET0pfjN]

It actually is reversing: I just changed the at() like you said with substr(index,1)
so to use:

cout << r_reverse("word.", 4) << endl;

You have to indicate to start at last position and I realized it should be:

string r_reverse(string originalString, int index)//NB: index is current last 
//	position in original string
{	
	if ( index < 0 )
		return "";//NOT return originalString.substr(index,1);
	else
		return originalString.substr(index,1) + r_reverse(originalString, index - 1 );
}

[4ET0pfjN]

It doesn't work btw with just appending * infront of function name...

[Vlykarye]

Then good job! You answered your own question!

[Vlykarye]

Well of course not. That's how you declare a function returning a pointer. You need to make the actual code inside the function return an actual pointer to get it to work.

[Vlykarye]

Also. I don't see any reason in returning a pointer. Can you state your reason for wanting this?

[4ET0pfjN]

for the sake of learning :)

[Vlykarye]

Ah ok. Then the way you are doing it cannot and should not return a pointer to a string, as there is no reason. However, it IS return a pointer to a character array (which is what a string basically is).

[Vlykarye]

This is how I would simplify your function:

string r_reverse ( string originalString )
{
    if ( originalString.size ( ) == 0 )
    {
        return "";
    }
    else
    {
        return originalString[originalString.size()-1] + r_reverse ( originalString.substr ( 0, originalString.size ( ) - 1 ) );
    }
}

Now we don't have to worry how long the string is.

[clanmjc]

Pass by const reference, no need for the copy:

string r_reverse ( const string &originalString )
{
    if(originalString.empty())
        return "";
    return originalString[originalString.size()-1] + r_reverse ( originalString.substr ( 0, originalString.size ( ) - 1 ) );
}

[Vlykarye]

Awesome. I was wondering what that error meant. Thanks for the info, clan!