Recursive function needs a return statement?

[boogerlad]

what's the difference
http://pastebin.com/331rMxcX
http://pastebin.com/ArwRs0h7

between those two? In the (recursive?) method "conversion", at the end
of an if, there is

return conversion(old);

and in the other version of the same program just

conversion(old);

Is there a difference in performance/syntax? Would this method even be
considered as recursion? Thanks again!

[Insectoid]

Both are essentially the same. The first runs conversion() and returns the result (old) right away, inside the if block. The other runs conversion() and then returns old at the bottom of the function.

[code]
function foo(a){
if (a) return a + 1;
}
//this is the same as:
function baz (a){
if (a) a += 1;
return a;
}

If Java supports tail-recursion optimization (I dunno if it does), then the first function will be much more efficient. Otherwise, they're the same.

[boogerlad]

ah, I see. Would http://pastebin.com/n6gMP18J be preferred because it's cleaner? Also, my google fu skills are weak, but can you explain tail recursion?

[Insectoid]

http://en.wikipedia.org/wiki/Tail_call

Basically, tail recursion is when the very last thing the function does is return the function call. This can be optimized in the build depending on the language and compiler, since you don't need to remember the stack. Regular recursion will build a copy of the function in RAM for each recurse- a function that recurses 10 times will have 10 copies of the function in RAM. With a tail call, since it's the last thing the function does, the function stack resets and is just re-run with the new input, so it only requires one copy of the function. In other words, it turns the recursive function into a loop.