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RE: Pipes Inside Mathematica?
*To*: mathgroup at smc.vnet.net
*Subject*: [mg45669] RE: [mg45659] Pipes Inside Mathematica?
*From*: "David Park" <djmp at earthlink.net>
*Date*: Sat, 17 Jan 2004 02:34:39 -0500 (EST)
*Sender*: owner-wri-mathgroup at wolfram.com
Harold,
There was a question similar to this just a few days ago.
{{5*Pi}, {13*E}} // IntegerPart //
Table[0, Extract[#, 1] // Evaluate, Extract[#, 2] // Evaluate] &
If you want to use a function that requires more than one argument after //,
then use a pure function. The only extra problem in this case is that Table
has the Attribute HoldAll so we also have to Evaluate the iterators.
David Park
djmp at earthlink.net
http://home.earthlink.net/~djmp/
From: Harold Noffke [mailto:Harold.Noffke at wpafb.af.mil]
To: mathgroup at smc.vnet.net
MathGroup:
I think Mathematica would be a better programming language if it had a
construct that allowed pipes (like Unix does). The //-mark comes
close to facilitating this, but Mathematica needs a placeholder to
denote "result from preceding //-mark".
Here's a short example to illustrate what would be gained.
In[1]:= m = 5*Pi // IntegerPart
Out[1]= 15
In[2]:= n = 13*E // IntegerPart
Out[2]= 35
In[3]:= Table[0, {m}, {n}] // MatrixForm
Out[3]//MatrixForm=
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0
> > 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
: :
: :
: :
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
0 0 0
> 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
What we would really like to write is the preceding computation as a
pipeline, so that it looks something like this ...
{{5*Pi},{13*E}} // IntegerPart // Table[0, Extract[<?>,1],
Extract[<?>,2]] // MatrixForm
The <?> symbol means, "I don't know what to put here" -- it's a
placeholder for whatever Mathematica wants to use as "result from
preceding //-mark". Maybe @ would make a good placeholder here, and
what we would see on screen is ...
{{5*Pi},{13*E}} // IntegerPart // Table[0, Extract[@,1], Extract[@,2]]
// MatrixForm
I think Mathematica will be a better programming language if it adopts
some sort of pipe convention.
Harold
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