Conversation

LSB

@luisobo

·

Oct 6, 2015

Is AutoLayout turing complete?

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LSB

@luisobo

·

Oct 6, 2015

@rob_rix

do you have any thoughts on this?

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Rob Rix‎

@rob_rix

·

Oct 7, 2015

@luisobo

It is not.

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LSB

@luisobo

·

Oct 7, 2015

@rob_rix

would love to here why

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Rob Rix‎

@rob_rix

·

Oct 7, 2015

@luisobo

Autolayout constraints model linear constraints of the form y = mx + b. This would be an extremely limited model of computation.

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Rob Rix‎

@rob_rix

·

Oct 7, 2015

@luisobo

Among other things, there’s no way to recurse, and there are no conditions.

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Rob Rix‎

@rob_rix

·

Oct 7, 2015

@luisobo

However, since you can embed non-AL layout in the same view hierarchy, you can compose linear constraints w/ other computation.

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Rob Rix‎

@rob_rix

·

Oct 7, 2015

@luisobo

But that doesn’t make AL Turing-complete; it just reflects that ObjC/Swift are.

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Rob Rix‎

@rob_rix

·

Oct 7, 2015

@luisobo

Further: I don’t know but I’ve been told

@kongtomorrow

’s got AL down cold

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Ken Ferry

@kongtomorrow

·

Oct 7, 2015

@rob_rix

@luisobo

haha. Hm. If you rely on pixel integralization, can make var a that has to be 0 or 1. Then notA = -a + 1. Then 3SAT.

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Andy Matuschak

@andy_matuschak

Replying to

@kongtomorrow

@kongtomorrow

@rob_rix

@luisobo

This is fucking gorgeous.

5:42 PM · Oct 7, 2015·Tweetbot for Mac

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Likes

Ken Ferry

@kongtomorrow

·

Oct 7, 2015

Replying to

@andy_matuschak

@andy_matuschak

@rob_rix

@luisobo

…but wrong. :-) AL doesn't do https://en.wikipedia.org/wiki/Integer_programming…. It finds a close _problem_ that has int solutions.

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Ken Ferry

@kongtomorrow

·

Oct 7, 2015

@andy_matuschak

@rob_rix

@luisobo

I was kinda proud of that approach. Didn't see it in the literature! Also not explainable in tweets. :-)

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