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Re: Argument types

• To: mathgroup at smc.vnet.net
• Subject: [mg5402] Re: Argument types
• From: dreece at atl.mindspring.com (Daryl Reece)
• Date: Thu, 5 Dec 1996 14:50:35 -0500
• Organization: MindSpring Enterprises, Inc.
• Sender: owner-wri-mathgroup at wolfram.com

Olivier Georg <olivier.georg at studi.epfl.ch> wrote:

>I recently disovered that you could specify the type of the arguments
>of a function being defined.  For exemple, f[x_Integer] if you want x 
>to be an integer.  There's also List, Real, Complex and Symbol.  But
>there's also ?MatrixQ which is not in the Mathematica book, to specify
>a matrix.  Are there other types?

This form of checking applies the function MatrixQ to expression x and
allows the argument to pass only if the result is True.  As a result
you can write your own functions to preform the check.

For example:

TriadQ[x_List] := (Length[x]===3);
 
F[x_?TriadQ] := ...

To answer your original question NumberQ, IntegerQ, EvenQ, OddQ,
PrimeQ, PolynomialQ, VectorQ and MatrixQ are the built in functions I
know.

-Daryl