[Jprogramming] Request for comments: multiple assignment

['Pascal Jasmin' via Programming]

pretty much any use of =:

(newrec ;reclookup) update assignwith 'database'



________________________________
From: Raul Miller <rauldmiller at gmail.com>
To: Programming forum <programming at jsoftware.com> 
Sent: Tuesday, July 11, 2017 9:36 AM
Subject: Re: [Jprogramming] Request for comments: multiple assignment



In what sort of cases are in-place optimizations a relevant issue for
assigning default values?

Thanks,

-- 
Raul


On Tue, Jul 11, 2017 at 9:06 AM, 'Pascal Jasmin' via Programming
<programming at jsoftware.com> wrote:
> The way I handle that,
>
> assignwithC
> 2 : 0
> (y) =: u (y~ [ ]) :: (n"_) 1
> :
> (y) =: x u (y~ [ ]) :: (n"_) 1
> )
>
>
> I think the call for =:: and =.. is based on 2 things.
>
> 1.  Although defaults and "ORvals"/unassigned default values can be handled easily enough through J expressions, for 805 anyway, it lost any inplace optimizations.
>
> 2. it only works for =: and not =.
>
>
>
> ________________________________
> From: Marshall Lochbaum <mwlochbaum at gmail.com>
> To: programming at jsoftware.com
> Sent: Tuesday, July 11, 2017 4:02 AM
> Subject: Re: [Jprogramming] Request for comments: multiple assignment
>
>
> Does this scheme support easily assigning a default value to a variable,
> that is, assigning only if the name is currently unused? This is a
> common case for me and I'm just now realizing that the "default" option
> doesn't really do that.
>
> See https://github.com/mlochbaum/JSound/blob/master/wav.ijs for an
> example, where I'm forced to write an awkward line of code to set the
> default format to 16-bit 44.1kHz. This seems easy enough to support with
> another trailing character on the name, like ^ or ?. So I would write
>    'FMT? F?' =: 1 16;44100
> instead of the current version.
>
> On a side note, Earl Grey is a good language to look at if you are
> interested in more sophisticated assignment schemes. I don't know if
> much of it is relevant to J, but it's very cool to see what can happen
> if you build a language to handle pattern matching from the bottom up.
> See http://www.earl-grey.io/doc.html, up to the section on pattern
> matching.
>
> Marshall
>
> On Tue, Jul 04, 2017 at 01:40:52AM -0400, HenryRich wrote:
>> Here is a feature that I have wanted for a long time:
>>
>> http://code.jsoftware.com/wiki/System/Interpreter/Requests#Expanded_Multiple_Assignment
>>
>> It attempts to solve the problem of moving verb arguments into
>> variable-names.  Allows defaults and multilevel arguments.  I will implement
>> this within a month or so, so get your comments in ASAP.
>>
>> Henry Rich
>>
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