No method in multimethod 'fmap' for dispatch value: class clojure.lang.PersistentVector$ChunkedSeq about amazonica HOT 9 CLOSED

0.1.2 will let you pass a lazy-sec

https://github.com/clojure/algo.generic/blob/master/src/main/clojure/clojure/algo/generic/functor.clj

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Am I doing something stupid here?

With a fresh clone of the repo and lein repl I run these two commands:

(use 'amazonica.aws.autoscaling)
(create-launch-configuration :security-groups (seq ["hello" "world"]))

... and I still get that error.

from amazonica.

Try (lazy-seq) instead of (seq)
On Apr 2, 2014 8:04 AM, "Neil Prosser" [email protected] wrote:

Am I doing something stupid here?

With a fresh clone of the repo and lein repl I run these two commands:

(use 'amazonica.aws.autoscaling)(create-launch-configuration :security-groups (seq ["hello" "world"]))

... and I still get that error.

Reply to this email directly or view it on GitHubhttps://github.com//issues/42#issuecomment-39341442
.

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That worked but it still means users are going to have to consider adding vec or lazy-seq to every collection parameter they use with the library.

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I've created this issue to see what the algo.generic auther makes of it. Hopefully help you avoid having to do anything beyond changing the version.

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You would only have to wrap a ChunkedSeq in a vec or lazy-seq call, or some other concrete collection type that doesn't implement an interface supported by algo.generic.

Calling seq on a vector is basically the only way I see to get a ChunkedSeq. (with-meta produces one too but that's not really applicable to most cases.)

Can you show your actual call to map that's producing the ChunkedSeq?

In a repl you can see it's probably rare that you're going to be dealing with ChunkedSeqs

(class (map identity [1 2 3])) ;;clojure.lang.LazySeq
(class (map identity '(1 2 3))) ;;clojure.lang.LazySeq

(class (seq [1 2 3])) ;; clojure.lang.PersistentVector$ChunkedSeq
(class (lazy-seq [1 2 3])) ;;clojure.lang.LazySeq

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I see the issue you created on algo.generic. You could implement fmap for ISeq to handle this special case.

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clojure/algo.generic#4

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Sorry, I've worked out that it's not coming from map. I'm an idiot. The ChunkedSeq is coming from me doing (seq something-mapped) so I get nil in the case of an empty sequence (which is more convenient than having to check count or similar). My map examples are all giving back LazySeq.

I'll probably be able to just use the original mapped sequence, rather than the one which has gone through the seq.

However, now I see that you've done the work on algo.generic. You sir, are a legend!

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