(defn update-in*
[m [k & ks] f & args]
(let [k (if (and (instance? clojure.lang.Indexed m)
(integer? k)
(neg? k))
(+ (count m) k)
k)]
(if ks
(assoc m k (apply update-in* (get m k) ks f args))
(assoc m k (apply f (get m k) args)))))
(update-in* [1 [1 2 [1 2 3]]] [-1 -1 -1] (constantly 5))
https://gist.github.com/wagjo/9813500
On Thu, Mar 27, 2014 at 6:17 PM, Mark Engelberg <mark.engelb...@gmail.com>wrote:
> Or you could write your own custom version of update-in that recognizes
> the keyword ::last to have a special meaning, so you could do:
>
> (update-in [1 2 ::last 1 ::last] ...)
>
>
> On Thu, Mar 27, 2014 at 8:57 AM, Jozef Wagner <jozef.wag...@gmail.com>wrote:
>
>> Calling count on vector is a constant time operation, so I think (dec
>> (count v)) is an acceptable and even idiomatic in this case. Make it a
>> function if it is too verbose for you.
>>
>> (let [assoc-last #(assoc % (dec (count %)) %2) ] (update-in [1 [1 2 [1 2
>> 3]]] [1 2] #(assoc-last % 5)))
>>
>> Jozef
>>
>>
>> On Thu, Mar 27, 2014 at 3:49 PM, Andy Smith <the4thamig...@googlemail.com
>> > wrote:
>>
>>> Hi,
>>>
>>> (1)
>>> I'm sure there must be a simpler way to update the last element of a
>>> vector other than dec and count :
>>>
>>> (let [xs [1 2 3]] (assoc xs (dec (count xs)) 4))
>>>
>>> This gets messy when updating vectors in nested data structures :
>>>
>>> (update-in [1 [1 2 [1 2 3]]] [1 2] #(assoc % (dec (count %)) 5))
>>>
>>> So, what am I doing wrong?
>>>
>>> P.S. I know I could reverse the order of the data in the lists (i.e.
>>> probably changing to lists rather than vectors for conj-ing purposes), but
>>> im interested in vectors specifically.
>>>
>>> Thanks
>>>
>>> Andy
>>>
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