>Because that's how you transform a recursive call into an iterative one, not nested for loops. I came to understand recursion through nested for-loops, though

>Because that's how you transform a recursive call into an iterative one, not nested for loops. I came to understand recursion through nested for-loops, though, but that might just be a historical accident. In the summer of 1988 I had written a Mastermind solver in Microsoft Quickbasic[1] for the specific case of 4 "pegs". At each guess, I used for-loops nested 4 deep to build a structure representing the possible remaining solutions (for all possibilities of the first peg, check all for the second peg, etc.) Then I wanted to extend it to work with variable numbers of pegs; after spending most of that summer trying to figure out a loop-based solution, I discovered that subroutines could call themselves and it hit me that I could have a function that took the possibilities already computed for a peg, and then called itself with those applied to the next peg. So I've always thought of recursion as a way to have arbitrarily deeply nested loops. [1] Believe it or not, it did support recursive functions!