CODEWITHSUNDEEP
structschemelispracket
Alexis Purslane
Alexis Purslane

Reputation: 1390

Racket struct error: given value instantiates a different structure type with the same name

I'm pretty familiar with Racket, and many in the Scheme and Lisp family, but I have no idea what is up with this error, or what is causing it:

network-biases: contract violation;
 given value instantiates a different structure type with the same name
  expected: network?
  given: (network ...) <-- I omitted this because its useless.

Heres the function where the error is (I have a gist of the rest):

(define (update-mini-batch net mini-batch eta)
  (define nabla-b (map (lambda (b)
             (apply grid (shape b))) (network-biases net)))
  (define nabla-w (map (lambda (w)
             (apply grid (shape w))) (network-weights net)))

  (define-values (nabla-b-new nabla-w-new)
    (foldl (lambda (lst bw)
       (define x (first lst))
       (define y (second lst))
       (define-values (nabla-b nabla-w) bw)
       (define-values (delta-nabla-b delta-nabla-w) (backprop net x y))

       (define nabla-b-new (+/ nabla-b delta-nabla-b))
       (define nabla-w-new (+/ nabla-w delta-nabla-w))
       (values nabla-b-new nabla-w-new)) (values nabla-b nabla-w) mini-batch))

  (struct-copy network net
           [biases (map (lambda (b nb)
                  (- b (* nb (/ eta (length mini-batch)))))
                (network-biases net) nabla-b-new)]
           [weights (map (lambda (w nw)
                   (- w (* nw (/ eta (length mini-batch)))))
                 (network-weights net) nabla-w-new)]))

I couldn't get an MCVE that actually threw an error, so I don't have one to give.

The distilled basics of what I'm trying to do in the above function is this:

- Thanks!!

Upvotes: 1

Views: 213

Answers (1)

soegaard
soegaard

Reputation: 31145

Structures in Racket are generative. This means that each time

(struct network (num-layers sizes biases weights) #:transparent)

is run, a new type of structure is created. These are all named network.

The error message you see is usually due to evaluating the structure definition twice (and it is a bit confusing since the two types have the same name).

I can't see anywhere in your code that could lead to (struct network ...) being run twice. Are you using DrRacket or an alternative environment that doesn't reset namespace?

If I open "nn.rkt" and run it, will I see the error?

Upvotes: 1

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