Returning from a function inside when statement

Question

All I'm trying to do is use a when statement to return a value :( I want the functionality of:

if(x)
    return y

And I'm trying to use:

(when (x) y)

But the when statement is not evaluating in a way that exits the function and return y. It just happily carries on to the next line. Is there a way to do this without making an extremely ugly looking if-else block? mzscheme/racket does not allow 1-armed ifs.

Answer 1

A simple way in Racket:

(define (foo x)
  (let/ec return
    (when (= x 0)
       (return 'zero))
    'not-zero))

Here ec stands for escape continuations, which are cheaper than full continuations.