Talk:Switch statement
From Wikipedia, the free encyclopedia
Just out of curiosity does anyone actually know the mechanics behind a switch statement? In other words how does a switch statement look in assembly? is it a jump, or a continuous set of conditionals?
I suppose this illustrates what im asking
int foo (int i) {
switch (i)
{
case 1: return 1;
case 2: return 2;
...
case n: return n;
default: return 0;
}
}
look the same as a whole lot of:
if else if else if
or would it jump immediately to the correct code? (i.e. actually switch) if it does switch, could someone explain how this works?
155.232.128.10 10:19, 24 January 2007 (UTC)
- Naturally, it's not dictated by the language. (Or at least not by C). It is certainly correct for a compiler to emit a long chain of if, else if, else if... but it is possible to do much better. For example, the compiler can use the control variable as an index into a jump table. Of course in the example you cite above, the programmer would do much better simply to return n; without using a switch at all. ;) Psyno 02:00, 8 March 2007 (UTC)
- It's a good question, and actually I think the article could use a section on that from an expert. The reason I think it's worth mentioning is that it's possible that it affects the performance of the program. When you are able to use a switch statement, is that better performance-wise than simply using a chain of "if" statements? I think there should be a discussion on that in the article by someone knowledgeable. Even if the answer is no, it is still worth mentioning in the article that the switch statement exists for reasons like code readability and there is no performance difference.
- Mbarbier 05:14, 25 March 2007 (UTC)
