CODEWITHSUNDEEP
lambdascheme
James Raitsev
James Raitsev

Reputation: 96391

Defining scheme functions with and without lambdas, is there a difference

Consider 2 Scheme functions

; Define function
(define (square n) (* n n ))
(square 12)
144

; Another way to define same function
(define square (lambda (n) (* n n)))
(square 12)
144

Both seem to produce the same result.

Is there any functional difference between these function declarations? Should one be preferred over another in some situations?

Upvotes: 3

Views: 126

Answers (2)

robbyphillips
robbyphillips

Reputation: 971

sepp2k is absolutely correct in that the two procedures you define are identical. In simple procedure definitions like this either is correct and it comes down to a matter of preference.

One case where it does make sense to use an explicit lambda statement is if you need to keep track of some sort of state in the procedure. For example, we could make a counter like this:

(define counter
    (let ((count 0))
      (lambda ()
          (set! count (+ count 1))
          count)))

(counter) ;=> 1
(counter) ;=> 2
(counter) ;=> 3

Upvotes: 1

sepp2k
sepp2k

Reputation: 370162

There is no difference between the two definitions - the former is syntactic sugar for the latter.

Which one you prefer is a matter of style, but my impression is that the former is generally the preferred way of defining functions as it is somewhat more succinct and perhaps also more readable.

Introductory texts often use the latter to make it clear that a named function is simply a variable holding a lambda - something that's not that clear when using the first variant.

Upvotes: 4

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