Re: [boost] boost.numeric (and multi_array)

From: Jeremy Siek (jsiek_at_[hidden])
Date: 2001-03-25 14:25:32

Hi Larry,

Sounds like there are some interesting ideas here, though I must admit I'm
having trouble getting though all the abbreviations and strange semi-colon
placement.

Here's what I got out of it:

from(s)   equivalent to Blitz's  Range(s,all)
upto(f)   equivalent to Blitz's  Range(all,f)
frto(s,f) equivalent to Blitz's  Range(s,f)

nextAx()  not sure what this does...

And an expansion vector is basically a utility class that includes all the
information necessary to specify an arbitrary sub-array of some multi-dim
array?

What I like here is the ability to string-along slicing information in a
convenient manner. I've been thinking along the same lines. However, I
think we can find a notation that will be understood more easily by
main-stream programmers.

Cheers,
Jeremy

On Thu, 22 Mar 2001, Larry Evans wrote:
jcampb> 
jcampb> I used to be an apl fan, and tried emulating some of apl's
jcampb> interface's with some c++ classes using expansion vectors
jcampb> described in _An APL Compiler_ by Timothy Budd(1988).  
jcampb> Operations on the expansion vector (size = rank) can be
jcampb> used to take a slice, rotate the axes.
jcampb> 
jcampb> Attached are a test driver _conslivar.c and a header file,
jcampb> varslirnk.h, declaring a class used to manipulate the
jcampb> expansion vector.  You may find the test driver cryptic,
jcampb> so I'll give some explanation.
jcampb> 
jcampb>     ; sout<<"===>ConSliOwn CTOR() via SliceOp: From(1)<<UpTo(2)"<<endl
jcampb>     ; ConSliOwn<double> ownSl(testArr<<From(1)<<UpTo(2)<<EndSli())
jcampb>     ; sout<<ownSl<<endl
jcampb> 
jcampb> I think this takes a slice out of testArr which drops the
jcampb> 1st element in axis 1, and then takes the 1st 2 elements
jcampb> of axis 2.  This is equivlent to the apl:
jcampb> 
jcampb>     ownS1 <- 2take[2]1drop[1]testArr
jcampb> 
jcampb> For example if:
jcampb> 
jcampb>     testArr =
jcampb>        {{ 11 ,  12,   13}
jcampb>         , { 21,   22,   23}
jcampb>         , { 31,   32,   33}
jcampb>         }
jcampb> 
jcampb> then:
jcampb> 
jcampb>      ownS1 =
jcampb>         {{ 21,   22}
jcampb>         , { 31,   32}
jcampb>         }
jcampb> 
jcampb> The actual data in the array is stored in a T* for the template arg (e.g. double).
jcampb> Indexing uses the expansion vector and successive operator[](int) to index into this T*.
jcampb> 
jcampb> I found apl's interface very useful; so, I'm suggesting something similar for boost.
jcampb> 
jcampb> 
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jcampb>  
jcampb> 
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jcampb> 
jcampb> 

----------------------------------------------------------------------
 Jeremy Siek                        www: http://www.lsc.nd.edu/~jsiek/
 Ph.D. Candidate                  email: jsiek_at_[hidden]
 Univ. of Notre Dame         work phone: [phone]
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