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Re: Condition for pure functions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg59808] Re: [mg59797] Condition for pure functions
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Mon, 22 Aug 2005 02:48:28 -0400 (EDT)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <200508210751.DAA26612@smc.vnet.net>
  • Reply-to: murray at math.umass.edu
  • Sender: owner-wri-mathgroup at wolfram.com

Perhaps the following?

  ( UnitStep[#] Sin[#] + (1 - UnitStep[#]) Tan[#] )&

Better than your version with Which, you could use Piecewise, as in:

   Piecewise[{{Tan[#], # < 0}, {Sin[#], # â?¥ 0}}] &

(Piecewise may handled better by other functions than Which).

Wonseok Shin wrote:
> Hello everyone,
> 
> Suppose that f[x] is defined as:
> 
> f[x_ /; x > 0] := Sin[x];
> f[x_ /; x <= 0] := Tan[x];
> 
> How can transform the above definition into a pure function?
> 
> I know
> 
> f = Which[# > 0, Sin[#], # <= 0, Tan[#]] &
> 
> is a one solution.  But is there any clever way to use Condition (/;)
> instead of Which[...] ?
> 
> 

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
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University of Massachusetts                413 545-2859 (W)
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Amherst, MA 01003-9305


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