CODEWITHSUNDEEP
clojure
Chris Murphy
Chris Murphy

Reputation: 6509

Clojure, return arguments from a function that are then used directly in a hash-map

I want to return a list of arguments from a function and have them put straight into a hash-map. I'm using a vector to enclose these arguments, working under the assumption that only one value can be returned from a Clojure function. So on the return part of the call I am wanting to strip away the vector.

This is what the function is successfully returning: 

[:top-edge {3 [[0 0]]}]

As you can see if you strip away the vector you get something that should be able to be placed straight into a hash-map (because it has a key and a value):

:top-edge {3 [[0 0]]}

I have experimented with apply and flatten, and know that in some circumstances concat can be used for stripping away the outermost vector, but still have not found a solution.

For the moment I have left the code so it is not stripping away the vector, and the error message makes perfect sense: java.lang.IllegalArgumentException: No value supplied for key: [:top-edge {3 [[0 0]]}]

Edit: Question already answered, but just to show the actual code and what does and does not work. This does work: 

(conj {:rep (->Blob rgb pos)} (new-edge-map pos edge-keyword seg-id))

, and this does not:

{:rep (->Blob rgb pos) (apply hash-map (new-edge-map pos edge-keyword seg-id))}

The error I get is 'Map literal must contain an even number of forms'.

Upvotes: 2

Views: 237

Answers (2)

Diego Basch
Diego Basch

Reputation: 13069

From the documentation of hash-map:

Returns a new hash map with supplied mappings. If any keys are
equal, they are handled as if by repeated uses of assoc.

So, 

(apply hash-map [:top-edge {3 [[0 0]]}])
=> {:top-edge {3 [[0 0]]}}

Upvotes: 0

Lee
Lee

Reputation: 144136

You can use conj:

(conj {} [:top-edge {3 [[0 0]]}])

Upvotes: 1

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