Re: new functional operator

• To: mathgroup at smc.vnet.net
• Subject: [mg125643] Re: new functional operator
• From: DrMajorBob <btreat1 at austin.rr.com>
• Date: Sat, 24 Mar 2012 02:03:39 -0500 (EST)
• Delivered-to: l-mathgroup@mail-archive0.wolfram.com
• References: <jjfd6e\$7u7\$1@smc.vnet.net> <jjpakk\$ov1\$1@smc.vnet.net>

```I'd still have to go with

Composition[g, f] /@ {1, 2, 3, 4}

It's fewer keystrokes and emphasizes that you're composing one function
with another, and it's not hard to the right to left convention we've
ALWAYS used in math.

Bobby

On Wed, 21 Mar 2012 17:53:12 -0500, Barrie Stokes
<Barrie.Stokes at newcastle.edu.au> wrote:

> Hi Bobby
>
> I agree with your sentiments.  The folk who like {1, 2, 3, 4} // f /@ #
> & // g /@ # & are those who regret the passing of assembly coding by
> hand, which opened up programming to the great unwashed.
>
> Of course it can be immeasurably improved by the addition of some more
> characters, to wit:
>
> {1, 2, 3, 4} // (f /@ # & ) // (g /@ # &)
>
> But, what about my favourite?
>
> Map[ (s \[Function] g[ f[ s ] ]), {1, 2, 3, 4} ]
>
> Or, somewhat less attractive IMHO,
>
> (s \[Function] g[ f[ s ] ]) /@ {1, 2, 3, 4}.
>
> I like (s \[Function] g[ f[ s ] ])  because to me it is intuitive, to
> use your word. I don't have to recall the way Composition[ ] works, I
> just have to know what g( f( x ) ) means in mathematics, and the
> \[Function] arrow is at least more suggestive to me of its
> meaning/effect than such as // or /@ or @@ or @@@, etc. I can at least
> suspect that \[Function] means "goes to" or "becomes".
>
> Barrie
>
> PS
> I've enjoyed this thread, MathGroup!
>
>>>> On 21/03/2012 at 9:46 pm, in message
>>>> <201203211046.FAA27118 at smc.vnet.net>,
> DrMajorBob <btreat1 at austin.rr.com> wrote:
>> Here SIX several equivalent expressions from (IMHO) most intuitive or
>>
>> Composition[g, f] /@ {1, 2, 3, 4}
>>
>> {g[f[1]], g[f[2]], g[f[3]], g[f[4]]}
>>
>> g /@ f /@ {1, 2, 3, 4}
>>
>> {g[f[1]], g[f[2]], g[f[3]], g[f[4]]}
>>
>> Apply[Composition, {g, f}] /@ {1, 2, 3, 4}
>>
>> {g[f[1]], g[f[2]], g[f[3]], g[f[4]]}
>>
>> g@f@# & /@ {1, 2, 3, 4}
>>
>> {g[f[1]], g[f[2]], g[f[3]], g[f[4]]}
>>
>> Compose[g, f@#] & /@ {1, 2, 3, 4}
>>
>> {g[f[1]], g[f[2]], g[f[3]], g[f[4]]}
>>
>> {1, 2, 3, 4} // f /@ # & // g /@ # &
>>
>> {g[f[1]], g[f[2]], g[f[3]], g[f[4]]}
>>
>> The last is truly awful.
>>
>> Bobby
>>
>> On Tue, 20 Mar 2012 02:18:47 -0500, roby <roby.nowak at gmail.com> wrote:
>>
>>>> That creates a information fog that makes *all* Mathematica code
>>>> harder
>>>> to understand, and Mathematica much harder to learn than it used to
>>>> be.
>>>
>>> {1, 2, 3, 4} /// f///g
>>>
>>>
>>>> {1, 2, 3, 4} // f /@ # & // g /@ # &
>>>
>>> sorry but I absolutly can't agree with your opinion in this case, the
>>> former expression is more or less fogless and would be much easier to
>>> understand.
>>> The latter expression bears a lot of clutter.
>>>
>>> Robert
>>>
>>>
>>>
>>
>

--
DrMajorBob at yahoo.com

```

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