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Re: pattern test and default value

• To: mathgroup at smc.vnet.net
• Subject: [mg6003] Re: [mg5967] pattern test and default value
• From: seanross at worldnet.att.net
• Date: Sat, 8 Feb 1997 22:38:42 -0500
• Sender: owner-wri-mathgroup at wolfram.com

Marlies wrote:
> 
> Hi,
> 
> It is possible to do the following:
> 
> x_h:v (an expression with head h and default value v)
> 
> Can anyone tell me whether it is possible to have a pattern test like
> _?NumberQ  AND have a certain default value?
> 
> Regards,
> 
> Marlies Brinksma


Try 
x_:v/;NumberQ[x].  

I routinely use this format for things like testing for square matrices 
of a certain length and input parameter management.