Question

If i use hte following codes , will the compiler optimize it like a switch structure , which uses a binary tree to search for values ?

   if ( X == "aaaa" || X == "bbbb" || X == "cccc" || X == "dddd" )
   {

   }
   else if ( X == "abcd" || X == "cdef" || X == "qqqq" )
   {

   }

It’s just an example , there’s no pattern of what’s inside the quote symbol

UPDATE

Ok , X is a string , but i don’t really think it matters here , i just want to know , when everything inside the if was all about single variable , will it be optimized.

Answer 1

The values WILL be compared one after the other as it is a requirement of the || or, the short-circuit operator. So, here two things will happen:

• X will be compared one-by-one from right-to-left.
• There will be NO MORE comparisons after any comparison that succeeds (Since it is the short-circuit OR operator) i.e. in the following case

For example:

int hello() {
    std::cout<<"Hello";
    return 10;
}

int world() {
    std::cout<<"World";
    return 11;
}

int hello2() {
    std::cout<<"Hello2";
    return 9;
}

int a = 10;

bool dec = (a == hello() || a == world())
bool dec = (a == hello2() || a == hello() || a == world())

The output for the first statement will be:

Hello

as a == world() will not be executed, and for the second Hello2 Hello, as the comparisons keep on happening till the first success.

In case of the && operator, the comparisons keep on happening until the first failure (as that is enough to determine the outcome of the entire statement).