Understanding recursion in the function normalize-definition form the racket sources

[Dan Synek]

I am trying to implement a variation of define. In order to do that I am trying to understand the source of the define macro in racket.

 It calls a function normalize-definition which looks like this:

  (define-values (normalize-definition)

    (case-lambda 

     [(stx lambda-stx check-context? allow-key+opt?)

      (let-values ([(id mk-rhs body)

                    (normalize-definition/mk-rhs stx lambda-stx check-context? allow-key+opt? #t)])

        (values id (mk-rhs body)))]

     [(stx lambda-stx check-context?) (normalize-definition stx lambda-stx check-context? #f)]

     [(stx lambda-stx) (normalize-definition stx lambda-stx #t #f)])))

In the two last cases of the case-lambda there is a call to normalize-definition. It is not a recursive call, since define-values cannot be used recursively. I cannot find any other normalize-definition in the modules required by the norm-define module.

 If I try to enter a copy of the definition (renamed to normalize-definition1) I get (as expected) that normalize-definition1 is undefined.

What is going on?

Thanks

Dan

[John Clements]

I’m confused by your assertion that define-values can’t be used recursively. Here’s a program that does this:

#lang racket

(define-values (fact)
(λ (x) (if (= x 0) 1 (* x (fact (sub1 x))))))

(fact 14)

Am I misunderstanding your message?

John Clements

> --
> You received this message because you are subscribed to the Google Groups "Racket Users" group.
> To unsubscribe from this group and stop receiving emails from it, send an email to racket-users...@googlegroups.com.
> To view this discussion on the web visit https://groups.google.com/d/msgid/racket-users/ce5ce36e-03ee-44b1-a5ae-4f5a6e7b9d1en%40googlegroups.com.

[Dan Synek]

(blush)

No you are not misunderstanding my question. I was wrong about define-values and confused by an error message related to normalize-definition not being known in another

part of the program due to phase problems. Thank you so much for taking the time to help me out!

Dan

[Wayne Harris]

Beginner here. I don't see the problem you seem to be referring to
here. In this example below, I recursively define arglen using
define-values.

#lang racket/base

(define-values (arglen)
(case-lambda
[() 'no-list]
[(ls) (if (null? ls)
0
(+ 1 (arglen (cdr ls))))]))

case-lambda-recursion.rkt> (arglen)
'no-list
case-lambda-recursion.rkt> (arglen (list))
0
case-lambda-recursion.rkt> (arglen (list 1))
1
case-lambda-recursion.rkt> (arglen (list 1 1))
2
case-lambda-recursion.rkt> (arglen (list 1 1 1))
3
case-lambda-recursion.rkt>