When to catch exceptions?

Question

Would there be any difference If i do the following without using exceptions?

void func()
{
    try
    {
        if (n > 5)
        {
            throw "n is greater than 5";
        }
    }
    catch (const char *e)
    {
        MessageBox(0, e, 0, 0);
        return;
    }
}

OR

void func()
{
    if (n > 5)
    {
       MessageBox(0, "n is greater than 5", "Error", 0);
       return;
    }
}

Answer 1

I would probably say that you best advised not to use exceptions for flow control. Exceptions, as the name suggests, are for handling exceptional circumstances. In the above case you're clearly expecting n to possibly be > 5 so it's not really an exceptional circumstance. If there is a way for your application to deal with that case, then it should do so in preference to raising an exception.

I'm sure there are cases where that logic falls down but in general I think that's a good rule of thumb.

But in technical terms there isn't much difference (possibly performance if you're doing it a lot).