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multi-dimensional indexing question #111

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rsc opened this issue May 9, 2022 · 3 comments · Fixed by #112
Closed

multi-dimensional indexing question #111

rsc opened this issue May 9, 2022 · 3 comments · Fixed by #112

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@rsc
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rsc commented May 9, 2022 •
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Originally posted by @fumin in #28 (comment):

Why does (5 5 rho iota 25)[3 2; 1 2 3] return the following?

11 12
13  6
 7  8

I was expecting

11 12 13 
6 7  8

which is also what's returned by https://tryapl.org/ with the expression (5 5 ⍴ ⍳ 25)[3 2; 1 2 3].

Below is my investigation 
(5 5 rho iota 25)[3 2; 1]
11 6

(5 5 rho iota 25)[3 2; 1 2]
11 12
 6  7

(5 5 rho iota 25)[3 2; 1 2 3]
11 12
13  6
 7  8
@rsc rsc mentioned this issue May 9, 2022
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rsc commented May 9, 2022

Definitely a bug. Will look into a fix.

rsc added a commit to rsc/ivy that referenced this issue May 9, 2022
@rsc
ivy: fix matrix index of matrix
fd1d151 
The right-to-left evaluation order for indexes was causing the
accumulation of the shape to end up reversed. Fix that by doing
an additional reverse after the loop.

Fixes robpike#111.
rsc added a commit to rsc/ivy that referenced this issue May 9, 2022
@rsc
ivy: fix matrix index of matrix
d2fe6f3 
The right-to-left evaluation order for indexes was causing the
accumulation of the shape to end up reversed. Fix that by doing
an additional reverse after the loop.

Fixes robpike#111.
@rsc rsc mentioned this issue May 9, 2022
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@rsc
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rsc commented May 9, 2022

Sent #112 with a fix.

@fumin
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fumin commented May 10, 2022

Thanks @rsc , I confirm #112 works for all the variants I can think of.
It's also good to see the internals of ivy in this change in action, enlightening! : )

robpike pushed a commit that referenced this issue May 10, 2022
@rsc
ivy: fix matrix index of matrix (#112)
df6b0d3 
The right-to-left evaluation order for indexes was causing the
accumulation of the shape to end up reversed. Fix that by doing
an additional reverse after the loop.

Fixes #111.
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ivy: fix matrix index of matrix rsc/ivy
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@rsc @fumin