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Re: Don't change my definition of a function

  • To: mathgroup at
  • Subject: [mg20746] Re: Don't change my definition of a function
  • From: Harald Giese <giese at>
  • Date: Wed, 10 Nov 1999 00:17:54 -0500
  • Organization: Institut fuer Meereskunde, Universitaet Hamburg
  • References: <803acp$>
  • Sender: owner-wri-mathgroup at

"Toshiyuki (Toshi) Meshii" wrote:
> Hi,
> I think Mathematica 4 (Win98) is changing the definition of a function every time I
> execute some procedures.
> Can somebody let me know what is happening?
> Here it is.
> I defined FM[x] as
> FM[x_]=1.122- 1.4 x +  7.33 x^2 - 13.08 x^3 + 14. x^4

Hi Toshi,

The reason for that behavoiur is, because you have used "=" instead of
":=" . The Mathematica online-help says:

Set (=)
lhs = rhs evaluates rhs and assigns the result to be the value of lhs.

SetDelayed (:=)
lhs := rhs assigns rhs to be the delayed value of lhs. rhs is maintained
in an unevaluated form. When lhs appears, it is replaced by rhs,
evaluated afresh each time. 


Harald Giese
Email: giese at
Phone: +49 (0)40 42838 5796; Fax: +49 (0)40 5605724
Institut fuer Meereskunde der Universitaet Hamburg
(Institute of Oceanography of the University of Hamburg)
Troplowitzstrasse 7, D-22529 Hamburg

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