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[Bug-apl] Dyadic Transpose

From: Louis de Forcrand
Subject: [Bug-apl] Dyadic Transpose
Date: Sat, 16 Jan 2016 17:57:28 +0000 (UTC)
User-agent: Loom/3.14 (http://gmane.org/)

I've been fiddling around recently and found that 
1 1⍉M should give the ¯1-slope diagonal of the 
matrix M (if 2 = ⍴⍴M). I've only tested this on rank
2 matrices, as I don't have enough experience to 
tell what it should do on higher rank arrays, but I've
found that dyadic transpose works as expected only
on matrices whose row index is greater or equal to
their column index.
More clearly:

≤/⍴M must give 1.

For example, this works:

M ← 2 3 ⍴ ⍳6 ◊ N ← 3 3 ⍴ ⍳9
(⊂1 1) ⍉¯ M N

But this gives an "Assertion failed" error:

N ← ⍉N or equivalently N ← 3 2 ⍴ ⍳6
1 1 ⍉ N

With large enough matrices (5 by 3 is enough), GNU
APL signals a segmentation fault and says Goodbye.

I will update when I've figured out exactly what is
supposed to happen to rank 3 or 4 arrays.

Good luck!

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