Scheme: calculating binary

Hey

I'm having a little problem while trying to make a piece of code that can turn a number into its binary code.

(define (displ-as-bin n)
(cond ((< n 1) (display " "))
((even? n) ((displ "0")(displ-as-bin (quotient n 2))))
(else ((display "1")(displ-as-bin (quotient n 2))))))

When trying it out, it gives me the correct answer, followed by an error, that I can't seem to fix!

For example:

(displ-as-bin 8 )
0001 . procedure application: expected procedure, given: #<void>; arguments were: #<void>

I can't figure out why I'm getting this error, so if anyone with a bit of Scheme knowledge could help me out here, it would be very much appreciated. Thanks =)

Hey,

You're trying to apply the return value of display which is #<void>. You can fix the code very simply by removing the brackets that are around this (to stop the application).

Here is the fixed code:



Notice how display and display-as-binary are both grouped within the conditions body automatically, there is no need for extra brackets .

Take care,

Mark.

Conversely, you could use (begin) to allow mutiple lines of code on a single (if) statement:


(Note that this prints the results in the correct order, too... however, it would make still more sense to generalize the code, by returning a string instead of simply displaying the value.)