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Re: Using a logical Or in the function definition

  • To: mathgroup at smc.vnet.net
  • Subject: [mg86698] Re: Using a logical Or in the function definition
  • From: "David Park" <djmpark at comcast.net>
  • Date: Wed, 19 Mar 2008 05:21:50 -0500 (EST)
  • References: <fro39q$i8a$1@smc.vnet.net>

You should use Alternatives (which is a pattern construction) instead of Or 
(which is a logical function). Also it is useful to use the symbol:(pattern) 
construction.

ab[r : (_Integer | _Rational), s : (_Integer | _Rational)] := r/s
{ab[3, 4], ab2[3/4, 3/4], ab[r, s], ab[3., 4.]}

-- 
David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark/


<ahallam at iastate.edu> wrote in message news:fro39q$i8a$1 at smc.vnet.net...
>I would like to use Or in the function definition as in
>
> ab[ Or[r_Integer,r_Rational], Or[s_Integer,s_Rational] ]:=r/s;
>
> In other words, I want the function to take integers or ratios of
> integers as arguments, but not real numbers which are not rational.
>
> But if I give the function integer arguments, it does not evaluate.
>
> If I try
>
> ar[ r_Integer , Or[s_Integer , s_Rational]] := r/s;
>
> and give an integer first argument it works and so on.
> 



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