Weird behaviour of "inline if"

Hello,

Can someone explain why "inline if" does not work in this particular example:

Code:

#include <iostream>
using namespace std;

string replaceStr(string source, char a, string b)
    {
    string result = "";

    for(int i=0; i<source.length(); i++)
        {
        char ch = source[i];


        // I have no idea why this doesn't work:
        // result += (ch == a) ? b : ch;

        if(ch == a)
            result += b;
        else
            result += ch;
        }

    return result;
    }


int main()
    {
    string s = "banana";

    cout << s << endl; // outputs: banana
    s = replaceStr(s, 'a', "--");
    cout << s << endl; // outputs: b--n--n--

    return 0;
    }

Looks like this "inline if" is really unhappy with different variable types (string and char), but if-else statement causes no errors.

I did this and it worked

Code:

#include <iostream>


using namespace std;
int main()
{
    char a='a';
    char b='b';

    string result ="";

    result +=  (a==b)? a : b ;


    cout<<result<<endl;

    return 0;
}

Also mind that it is not very efficient to have strlen as a condition if for loop, because every time you have to check the condition, you have to call strlen again and again, while calling it only once is enough.

So cache the result of strlen and use this in the condition.

Originally Posted by heinz55

Looks like this "inline if" is really unhappy with different variable types (string and char)

Because it can't decide which version of the operator+= to call.
That ambiguity is removed when you use the if statement explicitly.

[EDIT]
Actually, the issue seems to be more fundamental !
Operands of the ? operator are syntactically not allowed to be of different types.

Originally Posted by g++

operands to ?: have different types ‘char’ and ‘const char*’

The edit above was very helpful for me and i guess for the poster too.Bravo