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MathGroup Archive 1995

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Re: Equating a variable and its value

  • To: mathgroup at christensen.cybernetics.net
  • To: mathgroup at christensen.cybernetics.net
  • Subject: [mg1228] Re: Equating a variable and its value
  • From: jorma.virtamo at vtt.fi (Jorma Virtamo)
  • Date: Fri, 26 May 1995 03:29:57 -0400

jans at matematik.su.se (Jan Snellman) wrote:
>
> 
> Hello folks.
> 
> Study this codelet:
> 
> m=3; mult=Times[#,m]&; Clear[m]; mult[10]
> 
> To my dismay, I get 10 m, not 30.
> How can i convince Mathematica that only pedants make the distinction
> between a variable and its value?
> 
> Regards,
> Jan Snellman	jans at matematik.su.se
> 

In the constuction Times[#,m]& parameter m is not evaluated until 
the time of application of the function because of the non-standard 
evaluation rule of "Function" (see the Book, p. 279).

One possibility to overcome the problem is to write

mult = Function[x,x #]& [m]

Now m gets evaluated at the time of definition by the standard
evaluation procedure.


-- Jorma Virtamo


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