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Re: Using a logical Or in the function definition

  • To: mathgroup at smc.vnet.net
  • Subject: [mg86693] Re: Using a logical Or in the function definition
  • From: dh <dh at metrohm.ch>
  • Date: Wed, 19 Mar 2008 05:20:53 -0500 (EST)
  • References: <fro39q$i8a$1@smc.vnet.net>


Hi,

Or (abrev: ||)is a logical operator, not the alternative pattern 

operator Alternatives (abrev: |). Therefore, what you want:

ar[ r_Integer , Alternatives[s_Integer , s_Rational]] := r/s;

hope this hepls, Daniel





ahallam at iastate.edu wrote:

> 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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