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MathGroup Archive 2012

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Re: Pattern Syntax for Alternate Heads with Default Value

  • To: mathgroup at smc.vnet.net
  • Subject: [mg125844] Re: Pattern Syntax for Alternate Heads with Default Value
  • From: Bob Hanlon <hanlonr357 at gmail.com>
  • Date: Thu, 5 Apr 2012 05:45:01 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <201204040827.EAA29886@smc.vnet.net>

Clear[f]

f[x_Real: 2.5] = x^2;
f[x_Integer] = x^2;

{f[3], f[1.5], f[], f[I]}

{9, 2.25, 6.25, f[I]}

Clear[f]

f[] = 6.25;

f[x_Real | x_Integer] = x^2;

{f[3], f[1.5], f[], f[I]}

{9, 2.25, 6.25, f[I]}


Bob Hanlon

On Wed, Apr 4, 2012 at 4:27 AM, Ben <benp84 at gmail.com> 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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