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Re: Default and head in function argument

• To: mathgroup at smc.vnet.net
• Subject: [mg111623] Re: Default and head in function argument
• From: Leonid Shifrin <lshifr at gmail.com>
• Date: Sat, 7 Aug 2010 06:22:58 -0400 (EDT)

Hi,

Clear[f];
f[x : (_Integer?Positive) : 3] := x^3


Regards,
Leonid


On Sat, Aug 7, 2010 at 9:31 AM, NP <nomplume69 at gmail.com> wrote:

> Hi,
>
> I know how to define a function so that it evaluates only when the
> head of the argument is of a certain type:
>
> Clear[f];
> f[x_Integer?Positive] := x^3
> f[3]
> f[3.1]
> f[-3]
>
> 27
> f[3.1]
> f[-3]
>
> and I also know how to set default to an argument of a function like
> so:
>
> Clear[f]
> f[x_:3]
> f[]
>
> 27
>
> How do I do both i.e., specify head and default value?
>
> Thanks,
>
> NP
>
>