Convert lists into functions

Question

I have a little noob question. I have to do a homework on genetic programming in scheme and the first step is to finish some given functions.

I got to a point where i have to execute a randomly generated function with all the possible parameters in a range (using map). The "function" is list like '(* (+ 1 x) (- x (* 2 3))).

How can i execute it with a given parameter? (for example x = 2). By the way, the generated function has a maximum of 1 parameter (it's x or none).

Thanks!

C. K. Young · Accepted Answer · 2014-04-06 20:52:54Z

1

Here's my solution:

(define (execute expr)
  (lambda (x)
    (let recur ((expr expr))
      (case expr
        ((x) x)
        ((+) +)
        ((-) -)
        ((*) *)
        ((/) /)
        (else
         (if (list? expr)
             (apply (recur (car expr)) (map recur (cdr expr)))
             expr))))))

Example usage:

> (define foo (execute '(* (+ 1 x) (- x (* 2 3)))))
> (foo 42)
=> 1548

answered Apr 6, 2014 at 20:52

C. K. Young

224k47 gold badges394 silver badges446 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

Convert lists into functions

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related