CODEWITHSUNDEEP
racket
VansFannel
VansFannel

Reputation: 45911

Use or not, of lambda to define a function in Racket

I'm learning racket, and I used to use lambda to define my functions. But I have found that it is not needed to use it (as far as I know).

I have tried these two functions in DrRacket and both returns the same result:

#lang racket
(define factorial
  (lambda (number)
    (cond ((not (number? number))
           (error 'factorial "number is not a number"))
          ((equal? number 0)
           1)
          (else
           (* number (factorial (- number 1)))))))

(define (factorial1 number)
    (cond ((not (number? number))
           (error 'factorial1 "number is not a number"))
          ((equal? number 0)
           1)
          (else
           (* number (factorial1 (- number 1))))))

The second one, factorial1, doesn't use lambda.

Do I need to use lambda when I have to declare a function?

Upvotes: 2

Views: 368

Answers (1)

Magnus
Magnus

Reputation: 1282

As said in the comments, you don't need to use lambda. It is perhaps more conventional and convenient to use the non-lambda version to define a function

If you use the macro stepper in DrRacket, you can see how your program is expanded. (define (factorial1 number) etc.) becomes the following:

(define-values (factorial1)
 (lambda (number)
   (if (#%app not (#%app number? number))
     (let-values () (#%app error 'factorial1 (quote "number is not a number")))
     (if (#%app equal? number (quote 0))
       (let-values () (quote 1))
       (let-values () (#%app * number (#%app factorial1 (#%app - number (quote 1)))))))))

Interestingly, both define forms, the function definition and value ones, expand to define-values

Upvotes: 1

Related Questions