The dyad {&.> has ranks 0 0 .
In (<tgrade x) {&.> x the left argument
has rank 0 and so would agree with x .
Moreover, for atom i the computation is
< (><tgrade x) { > i{x which is correct.
In (tgrade x) {&.> x the left argument
has shape ,n and the right argument has shape ,c,
where n is the number of records in a column of x .
A length error is signalled if n~:c . Moreover,
even if n happens to be equal to c, the computation
for atom i is < (>i{tgrade x) { >i{x which is
not the right thing to do.
In the monad (tgrade x)&{&.> x the computation
for atom i is < (tgrade x)&{ >i{x , equivalent
to < (tgrade x) { >i{x , which is correct.
----- Original Message -----
From: bill lam
Date: Thursday, July 19, 2007 7:17
Subject: Re: [Jprogramming] multi column sorting
To: Programming forum
> thank you for pointer, a related question from that page
>
> why this work
> (<tgrade x) {&.> x
> but this will give length error
> (tgrade x) {&.> x
>
> I usually use the pattern (tgrade x)&{&.> x
>
> Sherlock, Ric wrote:
> > Have you checked Roger's Inverted Tables on the wiki? There's
> a section
> > there on grading & sorting.
> > http://www.jsoftware.com/jwiki/Essays/Inverted_Table
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