Truncating spaces off of the end of C++ style strings

[mohaakilla51]

OK, so I have a function that deals with strings, fixing them so that I can handle them easier. Here is the function:

string fix(string str)
{
       int length = str.size();
       for (int i = 0; i < length; ++i)
       {
           str[i] = tolower(str[i]);
       }
       
       for (int i = length; str[i] == " " || str[i]==0; --i)
       {
           str.erase(i);
       }
       return str;
}

the problem is, that it doesn't like the part where I truncate off the whitespace (or at least I try to, the method I am using is probably crap), it wont compile the second for loop, because

ISO C++ forbids comparison between pointer and integer

BTW, I am using Dev-C++ if that has anything to do with it.

So my question is, how would I do this? The reason I have to truncate the spaces is I am using getline, and have functions later on that count the length of the string...

[Ganon11]

While the last character is a ' ' (space) character, use the .substr() method to get the portion before the last character.

It's not efficient at all, but it's what I use.

[mohaakilla51]

yeah, but how would I do that?
[code=c]
while(str[str.length()-1]==' ')
{
str = str.substr(0,st r.length()-1);
}
[/code]
it tells me I cannot do that, but will let me do this:
[code=c]
while(str.subst r(str.length()-1,1)==' ')
{
str = str.substr(0,st r.length()-1);
}
[/code]
Can anyone tell me why?

But my original question has been answered, thank you.