[Dr. McKay]

My APCS teacher (this is Java, but basics) says that returning in the middle of a for is a bad idea, never never do it. He also dislikes break.

For instance, this checks if a value is in an array:

PHP Code:

public boolean found(String key) {
    for(String value : possibleFoos) {
        if(value.equals(key)) {
            return true; // he has a problem with this for some reason
        }
    }
    return false;
} 


Is this in fact a bad idea? Or is he just a moron?

[xPaw]

break is only used in loops and not anywhere else.
Returning inside a loop is perfectly safe.

[Dr. McKay]

Originally Posted by xPaw break is only used in loops and not anywhere else. Returning inside a loop is perfectly safe.

Thought so. He is an idiot.

For the record, he was saying that for this loop:

PHP Code:

for(int i = 0; i < max; i++) 


Instead of returning within the loop, you should set i to max so it exits the loop. WHICH IS THE SAME EXACT THING AS USING break;

*facepalm*

[matsi]

Seems like you should be the teacher then?

[fysiks]

Most people have some reason for saying such things. Ask him why. Sometimes it's more of a preference and they just don't want to deal with grading code that is not what he's used to.

[Dr. McKay]

Originally Posted by fysiks Most people have some reason for saying such things. Ask him why. Sometimes it's more of a preference and they just don't want to deal with grading code that is not what he's used to.

He doesn't even grade code. He just makes sure it runs.

[fysiks]

Originally Posted by Dr. McKay He doesn't even grade code. He just makes sure it runs.

I guess he is just stubborn in his ways then. It happens. Everybody has their opinions that they tell their pupils that it's "the correct way." It makes life easier for the teacher .

But, you would have to ask to see what he says to get a good idea of why he says what he does.

[asherkin]

Originally Posted by Dr. McKay Thought so. He is an idiot. For the record, he was saying that for this loop: PHP Code: for(int i = 0; i < max; i++)  Instead of returning within the loop, you should set i to max so it exits the loop. WHICH IS THE SAME EXACT THING AS USING break; *facepalm*

And more intensive since
a) it has to wait for the loop to complete (so no early exits) and then jump back up to the condition (not an issue in do..while, would be solved by optimization if not for: )
b) the compiler can't know you're exiting the look so it's fucking impossible for it to optimize (not as much an issue in Java where hardly any bytecode optimizations are done, but hey, it's all about leaning theory in the end!).

I don't think Java (at least not Oracle's compiler) does loop unrolling, but in a lot of compiled languages the compiler will replace the loop with a series of repeated blocks if it has a constant number of iterations (and if configured to prefer speed over size), this tells you just how much expensive jumps are to process. Manipulating the exit condition so it exits naturally just fucks all this up.

[Powerlord]

Originally Posted by asherkin I don't think Java (at least not Oracle's compiler) does loop unrolling, but in a lot of compiled languages the compiler will replace the loop with a series of repeated blocks if it has a constant number of iterations (and if configured to prefer speed over size), this tells you just how much expensive jumps are to process. Manipulating the exit condition so it exits naturally just fucks all this up.

My understanding is that the server JVM's JIT compiler (bytecode to native code) can do loop unrolling, but the source code to bytecode compiler doesn't.

[XINLEI]

I had the same question not so long about this. She explain me that "for" loops are useful when you know the start and the end of what are you going to do, although she dislikes returns in a for loop. Because she says it loses the main purpose of making for loops, and that's one of the reasons of why they are 3 ways to make loops.