[Jprogramming] Another Abbreviation

[Dan Bron]

Roger wrote:
> I suspect v"0 would serve.  If it 
> does not, I'd like to see what such a v is.

Viktor replied:
>     a =: 1 : '$ $ u@,'
>     v =: 5&,
> 
>     v"0 i. 2 2
>  [vs]
>     v a i. 2 2

Roger responded:
>  The intent of my question [was for]
>  some practical use that breaks 
>  the equivalence.

I cited some practical uses in [1] (and the last citation will tell you how
I found them, and how you might find others).  

One use is in JSoftware's standard library, where a matrix needs to be
passed to a library written in a less array friendly language, so the input
is raveled to vector, and the output reshaped into a matrix. 

On a historical note, both Kirk Iverson and I had something analogous to
UnderRavel in our personal utilities scripts.  So we must have found some
repeatable use for the pattern (though I admit I cannot remember an example
right now, and also my utilities script has collected some less-than-useful
specimens...)

-Dan

[1]  Earlier post in this thread:
http://www.jsoftware.com/pipermail/programming/2010-October/020648.html