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Re: using predefined expressions in functions [newbie question]

  • To: mathgroup at smc.vnet.net
  • Subject: [mg100219] Re: using predefined expressions in functions [newbie question]
  • From: Alexei Boulbitch <Alexei.Boulbitch at iee.lu>
  • Date: Thu, 28 May 2009 06:49:51 -0400 (EDT)

Hi, ChangMo,

Try to determine the function explicitly in terms of its arguments like one of the following:


f1[R1_, R2_] := R1.R2;

In[17]:= f1[{1, 2, 3}, {4, 5, 6}]

Out[17]= 32

or otherwise,

f2[x1_, y1_, z1_, x2_, y2_, z2_] := x1*x2 + y1*y2 + z1*z2;

In[25]:= f[1, 2, 3, 4, 5, 6]

Out[25]= 32

or like this:

In[35]:= 
f[x1_, y1_, z1_, x2_, y2_, z2_] := {x1, y1, z1}.{x2, y2, z2};

f[1, 2, 3, 4, 5, 6]

Out[36]= 32

Hi,

I've been trying to write a function using some predefined
expressions, but the function assignment seems to understand the
symbols in the expressions as literals. eg.,

Needs["VectorAnalysis`"]
R1 := {x1,y1,z1}
R2 := {x2,y2,z2}
f[x1_,y1_,z1_,x2_,y2_,z2_] := R1 . R2

f[1,2,3,4,5,6]

gives the output
x1 x2 + y1 y2 + z1 z2
instead of
32 ( = 1*4 + 2*5 + 3*6 )

Can anyone help me with this?  Thanks for your attention.


-ChangMo


-- 
Alexei Boulbitch, Dr., habil.
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