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Re: Re: Nesting functional commands

  • To: mathgroup at smc.vnet.net
  • Subject: [mg102968] Re: [mg102898] Re: [mg102875] Nesting functional commands
  • From: DrMajorBob <btreat1 at austin.rr.com>
  • Date: Thu, 3 Sep 2009 05:40:50 -0400 (EDT)
  • References: <200909010751.DAA18675@smc.vnet.net>
  • Reply-to: drmajorbob at yahoo.com

Better yet,

a = {1, 2, 3, 4};
Select[3 a, (# < 7 &)]

{3, 6}

As for how to "nest functional commands", my answer is simple: don't. It's  
never necessary, and it makes for less readable code.

Bobby

On Wed, 02 Sep 2009 02:59:25 -0500, Patrick Scheibe  
<pscheibe at trm.uni-leipzig.de> wrote:

> Hi,
>
> in this case it is easy. Just "say" how you want it with braces
>
> A = {1, 2, 3, 4};
> Select[(3*# & /@ A), (# < 7 &)]
>
> in other examples this would not work. Then you have the chance to use
> Function[{x,y,..},...] and it gets clear to Mathematica.
>
> Cheers
> Patrick
>
>
> On Tue, 2009-09-01 at 03:51 -0400, Erin Noel wrote:
>> Hi,
>>
>> So how would you go about nesting a functional command inside of another
>> functional command? For example, say A={1,2,3,4}, then 3*#&/@A =  
>> {3,6,9,12}.
>> No problem. But then what if, within that vector {3,6,9,12}, I wanted  
>> to use
>> the Select command to choose elements less than, say 7. The command
>> Select[3*#&/@A,#<7&] doesn't work because, as far as I can tell,  
>> Mathematica
>> doesn't know which "#" belongs to Select and which "#" belongs to the  
>> &/@
>> mapping over A. I know that I could define 3*#&/@A as a new variable and
>> then use that new variable in the Select command, but is there any way  
>> to
>> nest multiple commands in this way?
>>
>> Thanks a lot in advance,
>> Erin
>>
>>
>
>



-- 
DrMajorBob at yahoo.com


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