Question

I keep getting this error when trying to run the code:

(let ((exp lambda (x y) (if (= y 1) x (* (exp x (- y 1)) x)))))

Error:

let: bad syntax in: (let ((exp lambda (x y) (if (= y 1) x (* (exp x (- y 1)) x)))))

My function is supposed to define recursive exponentiation, but I’m having problems with let.

Answer 1

You’re missing an opening parenthesis before the lambda, and the let form is missing a body. Also, you can’t use let for defining recursive functions; you need to use letrec (for Scheme) or labels (for Common Lisp). Perhaps you meant this (Scheme):

(letrec ((exp (lambda (x y)
                (if (= y 1) x
                    (* (exp x (- y 1)) x)))))
  exp)