Nested If/Cond Scheme

Question

I'm having a hard time getting a simple nested if statement to work. I have two functions divisible2? and divisible3? and I want to see if a certain number - n is divisible by both 2 and 3. Here's what I have so far:

(define (divisible2? x)
  (zero? (remainder 2 x))) ;

(define (divisible3? x)
  (zero? (remainder 3 x))) ;

(define (div23 n)
  (if (divisible2? n)
    (if (divisible3? n)) #t (#f))
 )

Thanks

The order of the arguments for `remainder` is reversed, as I showed you in [this](http://stackoverflow.com/a/21272705/201359) answer, it should be `(remainder x 2)` and `(remainder x 3)` — Óscar López, Jan 22 '14 at 11:15

user2864740 · Accepted Answer · 2014-01-22T04:58:28.887

There are several problems. One is that the parenthesis are wrong around the inner-if such that it has no true-expr or false-expr within the form. The parenthesis around false later on are also problematic. In addition, every if should have both true-expr and false-expr supplied (although this differs in dialects, IIRC).

The symmetric structure can be seen in a corrected expanded form.

(if (divisible2? n)       ; outer if-expr
    (if (divisible3? n)   ; outer then-expr (and inner if-expr)
        #t                ; inner then-expr
        #f)               ; inner else-expr
    #f)                   ; outer else-expr

Alternatively, simply use and.

(and (divisible2? n) (divisible3? n))

And you could make the divisible? functions take in the "divisible by" value.

Nested If/Cond Scheme

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