In Scheme, how do you use lambda to create a recursive function?

Question

I\'m in a Scheme class and I was curious about writing a recursive function without using define. The main problem, of course, is that you cannot call a function within itse

Answer 1

I found this question because I needed a recursive helper function inside a macro, where one can't use define.

One wants to understand (lambda (x) (x x)) and the Y-combinator, but named let gets the job done without scaring off tourists:

 ((lambda (n)
   (let sub ((i n) (z 1))
     (if (zero? i)
         z
         (sub (- i 1) (* z i)) )))
 5 )

One can also put off understanding (lambda (x) (x x)) and the Y-combinator, if code like this suffices. Scheme, like Haskell and the Milky Way, harbors a massive black hole at its center. Many a formerly productive programmer gets entranced by the mathematical beauty of these black holes, and is never seen again.