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MathGroup Archive 1999

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Re: Early out with Map?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg16127] Re: [mg16036] Early out with Map?
  • From: Andrzej Kozlowski <andrzej at tuins.ac.jp>
  • Date: Sat, 27 Feb 1999 03:23:01 -0500
  • Sender: owner-wri-mathgroup at wolfram.com

On Sat, Feb 20, 1999, Oscar Stiffelman <ostiffel at leland.stanford.edu> wrote:

>Hi,
>
>Is it possible to interrupt Map before it reaches then end of the list?
>
>
>For example, how would I convert the following from procedural to
>functional?
>
>
>(* This is the procedural version *)
>foundSolution = False;
>For[i =1, i <= numChildren && ! foundSolution, i++,
>    If[testChild[children[[i]]],
>        foundSolution = True;
>      ];
>];
>foundSolution
>
>
>
>(*
>* This keeps going until it reaches the end of the list.
>* I would prefer to return as soon as testChild returns True
>*)
>Or @@ Map[testChild, children]
>
>
>(*
>* This does not actually return
>*)
>Map[If[testChild[#], Return[True], False]&, children]
>
>
>
>
Scan will do exactly what you want, If I have understood you correctly.
The way to use it is 

Scan[If[testChild[#],Return[True],False]&,children]

You will get True the first time Scan finds an element of children for
which testChild is True.

Andrzej Kozlowski
Toyama International University
JAPAN
http://sigma.tuins.ac.jp/
http://eri2.tuins.ac.jp/

Andrzej Kozlowski
Toyama International University
JAPAN
http://sigma.tuins.ac.jp/
http://eri2.tuins.ac.jp/



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