[Jprogramming] Dyads and identity function

[Pascal Jasmin]

a useful counterexample where 0 n $ y or i. 0 n produces a result that is conveniently different than i.0 0 would substantially contribute to the impression that the costs of eliminating that behaviour are high.  Especially, if there is no natural way of rewritting that counterexample.

I expect some performance costs in treating dyads "naturally" wrt identity functions.

I cannot measure the costs, and will stick to detailing benefits.  There would seem to be performance benefits from having values that are 'nil entity with rank k' (i.0 , i. 0 0, i.0 0 0 etc...) by not having to hold more complex data than necessary in memory, and not needing user code to guard against irrelevant details.

I couldn't understand the argument regarding {. and how it might be used, sorry.

but this made my head explode, (first answer is a fill, I presume, but still don't understand behaviour of last 2)
   {. i.0
0
   $ $ {. i.0 
0
   (i.0) -: $ {. i.0
1

I guess this example could be addressed:
   +/"1 |: 0 6 $ i.6
0 0 0 0 0 0

A shape of m 0 k1 k2 k3 could be converted to m 0 0 0 0, because as shown above, shapes of 0 k can easily be transposed into k 0.  There's still no 'real data' inside.  The only information is the shape.




----- Original Message ----
From: "Miller, Raul D" <rdmiller at usatoday.com>
To: Programming forum <programming at jsoftware.com>; Programming forum <programming at jsoftware.com>
Sent: Sunday, October 22, 2006 3:09:30 PM
Subject: RE: [Jprogramming] Dyads and identity function

Pascal Jasmin wrotete:

> I would suggest that the distinction between (0 n $ y1) and

> 0 0 $ y1 never provides any value and always "gets in the way".



If you are only building up lists using , that might be true. 

However, if you are manipulating collections using other operations,

such as {. then this is not at all true.



 



For what it's worth, here's an identity adjective:

   ident=:1 :'a:1 :(u b.1)'



For example:

   +ident 99

0

   +ident i. 9 9

0 0 0 0 0 0 0 0 0



-- 

Raul






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