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MathGroup Archive 2004

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Re: Re: bug in IntegerPart ?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg47987] Re: [mg47968] Re: bug in IntegerPart ?
  • From: "J. McKenzie Alexander" <jalex at lse.ac.uk>
  • Date: Tue, 4 May 2004 07:03:19 -0400 (EDT)
  • References: <200405040508.BAA17773@smc.vnet.net>
  • Sender: owner-wri-mathgroup at wolfram.com

On May 4, 2004, at 6:08 am, Bill Rowe wrote:

>> NO function affects evaluation of its arguments, or if one did, what 
>> would that look like?
>
> How about Plot? Plot does evaluate its arguments in a non-standard way 
> as compared to say Exp or Sqrt. So, some functions do affect the way 
> their arguments are evaluated.

In addition, some functions can have the attribute HoldFirst, whose 
sole purpose is to affect the evaluation of arguments. In the case of 
HoldFirst, the first argument isn't evaluated. Set has the attribute 
HoldFirst because if you evaluate

	m=10
	Set[m, 2*m]

you probably want to assign 20 to m, rather than attempt to assign 20 
to 10, which will produce an error because 10 isn't an lvalue.

Cheers,

Jason
--
Dr J. McKenzie Alexander
Department of Philosophy, Logic and Scientific Method
London School of Economics and Political Science
Houghton Street, London WC2A 2AE



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