Question

If I have a Boolean expression to check

(A && B)

If A is found to be false will the language bother to check B? Does this vary from language to language?

The reason I ask is that I’m wondering if it’s the case that B is checked even if A is false then wouldn’t

if (A) {
  if(B) {

  } else {
     // code x
  }
} else {
  // code x
}

be marginally quicker than

if (A && B) {

} else {
   // code x
}

Answer 1

This depends on the language. Most languages will implement A && B as a short-circuit operator, meaning that if A evaluates to false, B will never be evaluated. There’s a detailed list on Wikipedia.