Fun with recursion

just thought I'd share. Is there a better way?

string rev(string str)  //receives and returns a string
{

    if (llStringLength(str)==1) // end recursion when only 1 letter left
        { 
            return str;
        }
    else 
        {
        string front = llGetSubString(str, 0, 0); // first letter
        string rest = llGetSubString(str, 1, - 1);  // rest of string to end
        return rev(rest) + front;  // put the first letter at the back and reverse the rest.
        }

}

default
{
    state_entry()
    {

        llSay(0,rev("electroencephalograph"));
    }

}

Sure, 99% of all recursive algorythims can be written iteratively.

rev(string str) {
    string ret;
    integer i = llStringLength(str) - 1;
    for (; i >= 0; --i) {
        ret += llGetSubString(str, i, i);
    }
    return ret;
}

and is that one percent worth trying to learn recursion?

I think the thread title says it all: FUN with recursion! That's a fine reason.

(I suppose there are some computer science weenie reasons, as well. But: pshaw.)

IMO, it's usually a bad idea in an embedded-ish environment like LSL, because you can run out of memory pretty quickly. As a general programming tool, it is definitely useful, and sometimes the recursive algorithm is more elegant (and therefore easier to understand) than the equivalent iterative solution.

It is often much easier to describe the solution to a problem as a recursive algorithm. These solutions are often astonishingly easy to understand, too. And in many cases it is not that terrible important that the algorithm is the most "efficient" one around.

So the answer is: "Yes" It is even "worth trying to learn recursion" for those problems which have an iterative solution. The recursive one is simple more "elegant".

I've found recursion most useful in situations where you are working with a hierarchical data structure, such as a file system with folders or some other hierarchical categorization mechanism.

I also do not buy into using it when it can be done with loops and use less memory at the same time.

I'm specifically thinking of making a script that produces a maze and find that most algorithms use recursion. (plus a tower of hanoi might be fun)

It seems, as was said, that branching areas do better with recursion, while most linear problems have an easy iterative answer.

Mind you I'm just learning to program so my example of reversing text was just the first recursion I was able to do.

.... and I'd never seen the "Heap Collision" error so many times in my entire second life.

Recursion should be used carefully in LSL currently as the stack is so small .. if you're sure it'll bottom out after a few levels then it's probably OK.

I'm confident 100% of recursive algorithms can be written iteratively

Jesrad is right. All recursion can be converted to iteration. Now recursion is occasionally more elegant but in lsl where memory is an issue and we don't have any tree-esque datatypes with variable branches/lengths, It probably shouldn't be used.

The funnest way to write a recursive maze generator in SL would be to use llRezObject()/llGiveInventory() as the recursive call, and llSay()/llListen() as the return.

/me whaps argent over the head. bad ferret!

I demand one of you teach me scripting in compensation for making my head hurt so bad trying to read this!

You can't tell the difference between a ferret and an otter?

Just for that, I think I'll implement it and rez it in your shoes!