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Re: Problem overriding simple built-in functions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg28849] Re: Problem overriding simple built-in functions
  • From: phbrf at t-online.de (Peter Breitfeld)
  • Date: Tue, 15 May 2001 00:59:23 -0400 (EDT)
  • References: <9dld4j$o9b@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

Jean-Christophe Deschamps <jchd at worldnet.fr> schrieb:
> Hi,
> 
> I'm told the following occurs under Mathematica v4.0:
> 
> In[1]:= GCD[{3, 6}]
> Out[1]= {3, 6}
> In[2]:= GCD[x_List] := Apply[GCD, x]
> In[3]:= GCD[{3, 6}]
> Out[3]= GCD[{3, 6}]
> In[4]:= Apply[GCD, {3, 6}]
> Out[4]= 3
> 
> Why is it so? It looks like the override is ignored, but why?
> 
> The same exerpt seems to work fine under version 2.x.
> 
Jean-Christophe,
first you have to unprotect GCD (but I think you did this, else there
would be an error-message). Then define:

In[2]:= GCD[x_List]:=Apply[GCD,Sequence[x]]

Gruß Peter
-- 
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 Peter Breitfeld, Bad Saulgau, Germany   Meinen GnuPG/PGP-5x Key gibts dort



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