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Re: Pattern Syntax for Alternate Heads with Default Value

  • To: mathgroup at smc.vnet.net
  • Subject: [mg125878] Re: Pattern Syntax for Alternate Heads with Default Value
  • From: Christoph Lhotka <christoph.lhotka at fundp.ac.be>
  • Date: Thu, 5 Apr 2012 05:56:53 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <201204040827.EAA29886@smc.vnet.net>

hi,

to reproduce your example

f[(x_Real | x_Integer) : 2.5] := x^2;
where f[3] = 9
and f[1.5] = 2.25
and f[] = 6.25


I would separate the definitions like

f[] := 6.25
f[x_Real] := x^2
f[x_Integer] := x^2

to get from

{f[], f[3], f[2.25], f[x]}

the results

{6.25, 9, 5.0625, f[x]}.

best,

christoph


On 04/04/2012 10:27 AM, Ben wrote:
> I'm trying to build a unary function which accepts only arguments with
> two possible heads and has a default value.  That is, something like
> the following, except that this doesn't work.  Anyone know how to do
> this correctly?
>
> f[(x_Real | x_Integer) : 2.5] := x^2;
> where f[3] = 9
> and f[1.5] = 2.25
> and f[] = 6.25
>
>
>




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