Coding in Haskell

Programming Language class is alot of fun (sometimes). I spent part of the weekend studying for exams and playing with haskell. I realized I missed one part of the assignment after I submitted, but it was an interesting formatting issue. What's most interesting about functional languages is how concise the code is for some complex problem. Consider the following problem:

I have a list of strings and I want to put an element o after every n elements in the list, then convert the list to one space delimited string.

Lets try to do it in C++ :

string insertEvery(int n, string o, vector<string> & vs) {
	string res = "";
	int pos = 0;
	for(vector<string>::iterator it = vs.begin(); it != vs.end(); ++it) {
		res += *it;
		if(++pos % n == 0) {
			res += " " + o + " ";
		}
		else {
			res += " ";
		}
	}
	return res;
}

Next up C# (Kind of a different approach):

string insertEvery(int n, string o, List<string> list) {		
	for (int i = n; i < list.Count; i+=n) {
		list.Insert( i++, o );			
	}
	return string.Join( " ", list.ToArray() ).Replace( " " + o + " ", o );
}

And the winner...Haskell :

insertEvery n y [] = []
insertEvery n y x = (take n x) ++ [y] ++ insertEvery n y (drop n x)
insertEveryToString n y x = concat $ intersperse " " $ insertEvery n y x

I love the concise function definitions. Thinking totally recursive is hard at first, but once you get it everything just pieces together...