APL2: compress with nested arrays?
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APL2: compress with nested arrays?

In IBM APL2, you have to define a function to do compression
del R gets B COMPRESS A
R gets B/A del
And then use it with each:
C gets B COMPRESS each A

Sat, 23 Aug 1997 20:06:44 GMT
APL2: compress with nested arrays?

Quote:

>Subject: APL2: compress with nested arrays?
>Date: 7 Mar 1995 07:49:56 GMT
>I am looking for an APL2-expression which solves the following
>problem:
>A<-| |0 2 0| |1 0 0| |0 2 3| |
>I need an expression, which generates from the array 'A' the following
>array, whithout any loop, of course:
>   | |2| |1| |2 3| |
>I thought, I could use compression, but it doesn't work:
>Is there a simple solution for this problem?

In the problem you describe why not use the without function in strand
notation?

A <- A ~ [dieresis] 0

Don Wiss.

Sun, 24 Aug 1997 07:31:18 GMT
APL2: compress with nested arrays?
It is because / and \ represent operators, not functions, and in
expressions

data1 / data2

and

data1 \ data2

the "data1" item is an operand, not an argument -- which means they

can be punctuated

(data1/)data2     and     (data1\)data2

The function derivation happens before the application of the

derived function ...

--

Sun, 24 Aug 1997 13:57:15 GMT
APL2: compress with nested arrays?
I am looking for an APL2-expression which solves the following
problem:

+-------------------------+
| +-----+ +-----+ +-----+ |
A<-| |0 2 0| |1 0 0| |0 2 3| |
| +-----+ +-----+ +-----+ |
+-------------------------+

I need an expression, which generates from the array 'A' the following
array, whithout any loop, of course:

+---------------+
| +-+ +-+ +---+ |
| |2| |1| |2 3| |
| +-+ +-+ +---+ |
+---------------+

I thought, I could use compression, but it doesn't work:

B<-~A=0

C<-B/A or C<-B/{each}A or something like that.

Is there a simple solution for this problem?

Thanks Elmar.

--

Institute for Information Technology Systems | Tel: +49 231 755 4513
University of Dortmund                       | Fax: +49 231 755 3251
44221 Dortmund / Germany

Sat, 23 Aug 1997 15:49:56 GMT
APL2: compress with nested arrays?
Quote:

>  In IBM APL2, you have to define a function to do compression
>    del R gets B COMPRESS A
>    R gets B/A del
>  And then use it with each:
>    C gets B COMPRESS each A

Same with expand\replicate.  I think this is because the slashes
double up as symbols for the operators reduce and scan.  Other
functions should work as expected.

Sun, 24 Aug 1997 01:46:00 GMT
APL2: compress with nested arrays?

|> >I am looking for an APL2-expression which solves the following
|> >problem:
|> >A<-| |0 2 0| |1 0 0| |0 2 3| |
|>
|> >I need an expression, which generates from the array 'A' the following
|> >array, whithout any loop, of course:
|> >   | |2| |1| |2 3| |
|>

|> In the problem you describe why not use the without function in strand
|> notation?
|>
|>  A <- A ~ [dieresis] 0

Thank you. That is a solution I was looking for.
Sometimes the solution is so simple, that one don't see it.
In Germany we have a saying for it: 'Man sieht den Wald vor lauter
Baeumen nicht' which means in english: You don't see the forest
because of all the trees. :-)

Elmar.
--

Institute for Information Technology Systems | Tel: +49 231 755 4513
University of Dortmund                       | Fax: +49 231 755 3251
44221 Dortmund / Germany

Sun, 24 Aug 1997 15:44:31 GMT

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