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Make ** be right associative #9684

Merged
merged 1 commit into from
Oct 5, 2020
Merged

Make ** be right associative #9684

merged 1 commit into from
Oct 5, 2020

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asterite
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For https://forum.crystal-lang.org/t/exponentiation-operator-has-unexpected-behaviour/2457

I think it would be better if the associativity is the same as most major languages out there. And we better do this change before 1.0

@bcardiff
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Can we add a spec to settle also the -2 ** 2 case as explained by https://codeplea.com/exponentiation-associativity-options ?

As of 0.35.1 -2 ** 2 == 4, but in Ruby is -4.

@asterite
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Oh, that's totally unexpected for me, but I guess if most other programming languages, and even Google, work this way it makes sense to do it like that.

@bcardiff
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I also find it confusing :-). Even if we choose to leave as it is and behave differently from others a spec will settle the choice at least.

@asterite
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I don't know how to make it work :'-(

@asterite
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Feel free to try to make it work. It's already tricky as it is, but it's even more tricky with things like -2 ** 4 being parsed as -(2 ** 4), where -2 is parsed as a single token.

Maybe we can leave things as they are now, but document them well.

@asterite asterite closed this Sep 11, 2020
@asterite asterite deleted the exp-left-associative branch September 11, 2020 18:29
@radha
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radha commented Sep 12, 2020

Feel free to try to make it work. It's already tricky as it is, but it's even more tricky with things like -2 ** 4 being parsed as -(2 ** 4), where -2 is parsed as a single token.

Maybe we can leave things as they are now, but document them well.

Unary minus has a higher precedence than exponentiation in crystal. So it is expected -2 ** 2 == 4. In ruby the order is unary plus > exponentiaion > unary minus.

I think associativity of exponentiation and precedence of unary minus are separate problems.

@asterite
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Yes, I think they are separate problems too. Should we merge this and tackle the other problem later if needed?

@bcardiff
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Ok, sure.

@asterite asterite restored the exp-left-associative branch September 12, 2020 14:22
@bcardiff
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bcardiff commented Oct 5, 2020

@asterite I'm reopening this. I think we can merge this and change the ** associativity to match what most programming languages do as a convention.

Yet, I think the pr and code should be named right associative 🙈 . Left associative is what we have now.

Do you want to do the rename or should I?

@bcardiff bcardiff reopened this Oct 5, 2020
@bcardiff bcardiff added this to the 1.0.0 milestone Oct 5, 2020
@asterite asterite changed the title Make ** be left associative Make ** be right associative Oct 5, 2020
@asterite
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asterite commented Oct 5, 2020

should be named right associative 🙈

Oops! 😄

@asterite
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asterite commented Oct 5, 2020

Ready for another review... I can't change the branch name, though :-P

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👍

FYI, I continued the discussion of unary negation in the forum thread.

@asterite asterite merged commit 719d314 into master Oct 5, 2020
@bcardiff bcardiff deleted the exp-left-associative branch October 16, 2020 16:10
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3 participants