Re: Problem overriding simple built-in functions

• To: mathgroup at smc.vnet.net
• Subject: [mg28809] Re: Problem overriding simple built-in functions
• From: "Orestis Vantzos" <atelesforos at hotmail.com>
• Date: Mon, 14 May 2001 01:33:01 -0400 (EDT)
• Organization: National Technical University of Athens, Greece
• References: <9dld4j\$o9b@smc.vnet.net>
• Sender: owner-wri-mathgroup at wolfram.com

```GCD is a protected Symbol, so you can't add any new definitions.
Try Unprotect[GCD] first...and don't forget to Protect[GCD] after you make
the new assignment.
Orestis

"Jean-Christophe Deschamps" <jchd at worldnet.fr> wrote in message
news:9dld4j\$o9b at smc.vnet.net...
> 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.
>

```

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