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MathGroup Archive 2004

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RE: what's wrong about my package?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg45424] RE: [mg45391] what's wrong about my package?
  • From: "David Park" <djmp at earthlink.net>
  • Date: Wed, 7 Jan 2004 01:09:17 -0500 (EST)
  • Sender: owner-wri-mathgroup at wolfram.com

Andy,

In your last statement

BernsteinPolynomial[fx_, x_,n_] :=Module[{},Sum[Replace[fx,
x ->i/n]*Bernstein[i, n, t], {i, 0, n}]];

you introduced the symbol t and since this is introduced in the Private
section of your package it has the complete domain specification of

CAGD`Private`t

and that is what you are complaining about. But I have no idea what should
be there instead of t. If t is supposed to be a variable that is used in the
answer, you may want to replace the last call with

Bernstein[i, n, Global`t]

But it might be better to let the user pass the symbol he wishes to use.

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

From: ANDY [mailto:wangzhengyao at hotmail.com]
To: mathgroup at smc.vnet.net

hello,
i want to build a package about computer aided Geometirc design for me!

____________________________________
......
Begin["`Private`"]
Bernstein[i_, n_, v_] := Binomial[n, i]*(1 - v)^(n - i)*v^i

BezierCurve[pts : {{_, _} ..} | {{_, _, _} ..}, v_] :=
    Module[{n = Length[pts] - 1},
      Simplify[
        Table[Bernstein[i, n, v], {i, 0, n}].pts]
      ];

BernsteinPolynomial[fx_, x_,n_] :=Module[{},Sum[Replace[fx,
x ->i/n]*Bernstein[i, n, t], {i, 0, n}]];

End[]
EndPackage[]
___________________________________

 i want use BernsteinPolynomial to compute the Bernstein Polynomial of the
function fx (f(x)),but when i use it in mathematica,there are something
wrong:


In[28]:=
\!\(BernsteinPolynomial[x\^2 + x, x, 8]\)

Out[28]=
\!\(\((1 - CAGD`Private`t)\)\^8\ \((x + x\^2)\) + 8\ \((1 -
CAGD`Private`t)\)\
\^7\ CAGD`Private`t\ \((x + x\^2)\) + 28\ \((1 - CAGD`Private`t)\)\^6\ \
CAGD`Private`t\^2\ \((x + x\^2)\) + 56\ \((1 - CAGD`Private`t)\)\^5\ \
CAGD`Private`t\^3\ \((x + x\^2)\) + 70\ \((1 - CAGD`Private`t)\)\^4\ \
CAGD`Private`t\^4\ \((x + x\^2)\) + 56\ \((1 - CAGD`Private`t)\)\^3\ \
CAGD`Private`t\^5\ \((x + x\^2)\) + 28\ \((1 - CAGD`Private`t)\)\^2\ \
CAGD`Private`t\^6\ \((x + x\^2)\) + 8\ \((1 - CAGD`Private`t)\)\ \
CAGD`Private`t\^7\ \((x + x\^2)\) + CAGD`Private`t\^8\ \((x + x\^2)\)\)


Why?
how to correct it??
thank you?


Andy
2004.1.5






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