Tower of hanoi, python -> scheme, shows error. What am I missing?

The python implementation

import sys

def move(src, dst, tmp, num):
    if num == 1: print 'Move from', src, 'to', dst
        move(src, tmp, dst, num-1)
        move(src, dst, tmp, 1)
        move(tmp, dst, src, num-1)

move('left', 'right', 'middle', int(sys.argv[1]))

Gives the right solution for tower of hanoi. But my scheme port,

(define move
    (lambda (src dst tmp num)
      (if (= num 1) (printf "Move from ~s to ~s \n" src dst)
          ((move src tmp dst (- num 1))
           (move src dst tmp 1)
           (move tmp dst src (- num 1))))))

Gives the right solution but in the end throws the following error.

procedure application: expected procedure, given: #<void>; arguments were: #<void> #<void>

I know that its my print statement that is throwing the error, but I can't figure out why is this happening ?


 ((move src tmp dst (- num 1))
  (move src dst tmp 1)
  (move tmp dst src (- num 1)))

The above code doesn't do what you think it does :)

To execute a series of expressions / statements you need something like this:

((λ ()
  (move src tmp dst (- num 1))
  (move src dst tmp 1)
  (move tmp dst src (- num 1))))

The syntactic sugar in Scheme is

   (move ...)
   (move ...)
   (move ...)

((move ...) (move ...) (move ...))

will be evaluated, and the code seems to work. But as soon as the recursion ends, the interpreter will try to execute it as (op param1 param2) and there is where you get the error #<void>; arguments were: #<void> #<void>

Need Your Help

How to add hyperlink in pdf using pdfbox

java pdf pdf-generation pdfbox

I want to add a hyperlink in PDF created using PDFBOX, such that i click on some text example 'Click here' will redirect to URL. I tried using PDAnnotationLink and PDActionURI, but how to add it in

Control template for existing controls in WPF

.net wpf controltemplate

How to get existing control's controltemplate in WPF in XAML format(visual tree)?