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RE: Re: Problem overriding simple built-in functions

• To: mathgroup at smc.vnet.net
• Subject: [mg28839] RE: [mg28800] Re: [mg28796] Problem overriding simple built-in functions
• From: "David Park" <djmp at earthlink.net>
• Date: Tue, 15 May 2001 00:59:12 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

But what possible benefit was there in the first place in making GCD
listable?

David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/

> From: Andrzej Kozlowski [mailto:andrzej at tuins.ac.jp]
To: mathgroup at smc.vnet.net
>
> The reason for all this is thet GCD has the Attribute Listable:
> In[1]:=
> Attributes[GCD]
>
> Out[1]=
> {Flat,Listable,Orderless,Protected}
>
> This means that GCD[{2,3}] is just {GCD[2],GCD[3]} which is just {2,3}. In
> order for your over-ride to work you will have to clear the Listable
> attribute of GCD with ClearAttributes[GCD,Listable] . You will, of course,
> loose all the benefits of listability.
>
>
> --
> Andrzej Kozlowski
> Toyama International University
> JAPAN
>
> http://platon.c.u-tokyo.ac.jp/andrzej/
> http://sigma.tuins.ac.jp/~andrzej/
>
>
>
>
> on 01.5.13 4:28 PM, Jean-Christophe Deschamps at jchd at worldnet.fr wrote:
>
> > 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.
> >
> >
>
>