Re: Destructuring seems to work with PersistentList and not with PersistentVector

[Matching Socks]

In case it's not clear from the above, {:keys [...]} is a 
technique for *map* destructuring of associative data structures.

(let [{:keys [a b]} {:a 1 :b 2}] [a b])
[1 2]


As documented at http://clojure.org/reference/special_forms, :keys
takes a vector of the symbols to bind.

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Re: Destructuring seems to work with PersistentList and not with PersistentVector

[Nicola Mometto]

that's an implementation detail you should not rely on.
it only works to support keyword arguments to functions
On 23 Jan 2016 17:36, "Harold"  wrote:

> Hello,
>
> While destructuring yesterday, I encountered this difference:
>
> > (let [{:keys [:a :b]} '(:a 1 :b 2)] [a b])
> [1 2]
>
> > (let [{:keys [:a :b]} [:a 1 :b 2]] [a b])
> [nil nil]
>
> I have read some of the relevant documentation and some related blog
> posts, but I am still having trouble explaining this difference
> (destructuring seems to work with PersistentList and not with
> PersistentVector).
>
> Kind thanks in advance for any insight.
>
> Warmly,
> -Harold
>
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Re: Destructuring seems to work with PersistentList and not with PersistentVector

[Gregg Reynolds]

On Jan 23, 2016 11:36 AM, "Harold"  wrote:
>
> Hello,
>
> While destructuring yesterday, I encountered this difference:
>
> > (let [{:keys [:a :b]} '(:a 1 :b 2)] [a b])
> [1 2]
>
> > (let [{:keys [:a :b]} [:a 1 :b 2]] [a b])
> [nil nil]
>
> I have read some of the relevant documentation and some related blog
posts, but I am still having trouble explaining this difference
(destructuring seems to work with PersistentList and not with
PersistentVector).

The keys of a vector are ints.  In your second example, :a and :b are
values, not keys.

Gregg

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Destructuring seems to work with PersistentList and not with PersistentVector

[Harold]

Hello,

While destructuring yesterday, I encountered this difference:

> (let [{:keys [:a :b]} '(:a 1 :b 2)] [a b])
[1 2]

> (let [{:keys [:a :b]} [:a 1 :b 2]] [a b])
[nil nil]

I have read some of the relevant documentation and some related blog posts, 
but I am still having trouble explaining this difference 
(destructuring seems to work with PersistentList and not with 
PersistentVector).

Kind thanks in advance for any insight.

Warmly,
-Harold

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