On 2013.01.03 08:25:58, you,
the extraordinary Graham Parkhouse, spake thus:
> Subject: Re: Atop continues to puzzle me
>
>
> This post was initially titled 'The benefits of function composition'
>
...
> There are things you can achieve with function composition that cannot be
> achieved so elegantly any other way:
>
> 3 4 5<@#"0 i.3
> +-----+-------+---------+
> |0 0 0|1 1 1 1|2 2 2 2 2|
> +-----+-------+---------+
>
> This is what I want - a set of 3 0s, a set of 4 1s and a set of 5 2s.
>
> This doesn't give me what I want:
>
> 3 4 5#"0 i.3
...
>
> Nor does this:
>
> 3 4 5 ([: <"1 #"0) i.3
...
> But this does:
>
> each
> +--+-+
> |&.|>|
> +--+-+
> 3 4 5#"0 each i.3
> ... but then &. is function composition.
I thought there might be a way of getting a function
without using composition by using "L:" . But the
best I came up with was:
f=. (# L: 0) & <"0
3 4 5 f i.3
+-----+-------+---------+
|0 0 0|1 1 1 1|2 2 2 2 2|
+-----+-------+---------+
But the "&" vitiates the attempt.
The general argument about J functions having
to produce rectangular arrays should have
convinced me anyway.
NM
--
Nollaig MacKenzie
http://www.yorku.ca/nollaig
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