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## Re: [Bug-apl] The Dyalog ⌸ operator

 From: Alexey Veretennikov Subject: Re: [Bug-apl] The Dyalog ⌸ operator Date: Wed, 27 Apr 2016 07:12:58 +0200 User-agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.91 (darwin)

Hi,

If you are talking about Dyalog, you can take a look for example here:
http://help.dyalog.com/14.1/Content/Language/Introduction/Language%20Elements.htm

Christian Robert <address@hidden> writes:

> where are you taking the definition of various functions like ?
>
> power operator ?
>
> dieresis jot ? like: (⊂⍤1) z,⍪z  (I really don't know what it is doing)
>
> I see no references anywhere on the web. None in apl2 manual, none in Dyalog
> manual.
>
> how can I learn thoses ...  without a manual and/or some examples ?
>
>
> Xtian.
>
>
>
> On 2016-04-26 23:02, Elias Mårtenson wrote:
>> I was reading about the Dyalog "key" operator ⌸. It's certainly a useful
>> function, and something that should probably be added to GNU APL, in my
>> opinion.
>>
>> As always when thinking about useful additions to GNU APL, I wanted to try to
>> do some things that ⌸ can do, without having access to it.
>>
>> So, I wanted to simply take a string of characters, and create a list of each
>> character and the number of occurrences of each character in that string. My
>> solution works, but feels clumsy:
>>
>> *       { ⊃{(↑⍵) (↑⍴⍵)}¨(⎕UCS v) ⊂ v←⍵[⍋⍵] } "abcfoobat"*
>> ┏→━━━━┓
>> ↓'a' 2┃
>> ┃'b' 2┃
>> ┃'c' 1┃
>> ┃'f' 1┃
>> ┃'o' 2┃
>> ┃'t' 1┃
>> ┗━━━━━┛
>>
>> Can anyone improve this? In particular, can it be improved to the point of
>> convincing me that ⌸ is not needed?
>>
>> Regards,
>> Elias
>

--
Br,
/Alexey

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