String function won't return string

Question

I cant seem to return str in my RemSpacePunct function.

I wanted to make a function that removes spaces in a string but when I run the code, it won't remove the space.

string RemSpacePunct(string str);
string sort(string str);

int main(){ 
    string s = "partial men";
    
    sort(s.begin(), s.end());
    
    RemSpacePunct(s);   
    cout << s;  
}

string RemSpacePunct(string str)
{
    //add code here
    int s, i;
    
    s = str.length();
    
    for(i = 0; i < s; i++){
        if(isalnum(str[i]) == false){
            str.erase(i, 1);
        }       
    }   
    return str;
}

Answer 1

You're ignoring the return value. str is copied when it's passed to the function, so any modifications you perform on the argument aren't reflected back to the original value. Instead, you should return a modified value - which you do, but you then ignore it instead of using it:

string result = RemSpacePunct(s);   
cout << result;