Switch statement with returns — code correctness

Question

Let's say I have code in C with approximately this structure:

switch (something)
{
    case 0:
      return "blah";
      break;

    case 1:
    case 4:
      return "foo";
      break;

    case 2:
    case 3:
      return "bar";
      break;

    default:
      return "foobar";
      break;
}

Now obviously, the "break"s are not necessary for the code to run correctly, but it sort of looks like bad practice if I don't put them there to me.

What do you think? Is it fine to remove them? Or would you keep them for increased "correctness"?

Answer 1

If you have "lookup" type of code, you could package the switch-case clause in a method by itself.

I have a few of these in a "hobby" system I'm developing for fun:

private int basePerCapitaIncomeRaw(int tl) {
    switch (tl) {
        case 0:     return 7500;
        case 1:     return 7800;
        case 2:     return 8100;
        case 3:     return 8400;
        case 4:     return 9600;
        case 5:     return 13000;
        case 6:     return 19000;
        case 7:     return 25000;
        case 8:     return 31000;
        case 9:     return 43000;
        case 10:    return 67000;
        case 11:    return 97000;
        default:    return 130000;
    }
}

(Yep. That's GURPS space...)

I agree with others that you should in most cases avoid more than one return in a method, and I do recognize that this one might have been better implemented as an array or something else. I just found switch-case-return to be a pretty easy match to a lookup table with a 1-1 correlation between input and output, like the above thing (role-playing games are full of them, I am sure they exist in other "businesses" as well) :D

On the other hand, if the case-clause is more complex, or something happens after the switch-statement, I wouldn't recommend using return in it, but rather set a variable in the switch, end it with a break, and return the value of the variable in the end.

(On the ... third? hand... you can always refactor a switch into its own method... I doubt it will have an effect on performance, and it wouldn't surprise me if modern compilers could even recognize it as something that could be inlined...)

Answer 2

For "correctness", single entry, single exit blocks are a good idea. At least they were when I did my computer science degree. So I would probably declare a variable, assign to it in the switch and return once at the end of the function

Answer 3

Wouldn't it be better to have an array with

arr[0] = "blah"
arr[1] = "foo"
arr[2] = "bar"

and do return arr[something];?

If it's about the practice in general, you should keep the break statements in the switch. In the event that you don't need return statements in the future, it lessens the chance it will fall through to the next case.

Answer 4

I would take a different tack entirely. Don't RETURN in the middle of the method/function. Instead, just put the return value in a local variable and send it at the end.

Personally, I find the following to be more readable:

String result = "";

switch (something) {
case 0:
  result = "blah";
  break;
case 1:
  result = "foo";
  break;
}

return result;

Answer 5

What do you think? Is it fine to remove them? Or would you keep them for increased "correctness"?

It is fine to remove them. Using return is exactly the scenario where break should not be used.