[Haskell] Computus #679
[Haskell] Computus #679
Conversation
jiegillet
added
the
Implementation
| computus mode year = | ||
| let | ||
| -- Year's position on the 19 year metonic cycle | ||
| a = year `mod` 19 |
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type signatures are recomended for local bindings. They help you think and avoid crazy type errors on basic mistakes (as ghc will just try make it work somehow).
So consider adding: a :: Int
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Would that achieve anything? The signature of mod is mod :: Integral a => a -> a -> a and since year is an Int, a cannot possibly be anything else.
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If you make a mistake on writing implementations, having your code blotted with typesignatures will avoid crazy ghc deductions. It's more defensive. Typesignatures rarely do anything in haskell (1). It'sHindley–Milner all the way down.
(1): Bar some major exceptions from langauge extensions, such as datakinds, GADTs etc.
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But it would hinder readability I think. And since all the local bindings derive from year, it would do nothing.
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I don't mind going either way here. It looks like this conversation is the only one holding this PR back.
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Ah, I see the confusion, how about this:
a :: Int
a = year `mod` 19let blocks can have same typesignatures as functions. In fact, you can put functions in let blocks!
Don't worry about being stubborn, this is constructive in my opinion.
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I see this conversation is still going, so let me know when both of you are happy with the code!
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well, I"m not getting a reply so yes?
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I did reply, on May 24, on another comment. I tried what you suggested (with a twist).
EDIT: nope, that comment was for something else. I pushed a commit but did not comment. Sorry about that.
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| -- Finding the next Sunday | ||
| Easter -> | ||
| let |
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This is a knitpick: since haskell is lazy, there is no need for doing 2 of these let bindings, in fact I'd just throw all these variables in a big where block and put the logic (case mode of ... if then) at the top. This avoids the nesting
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I chose this way because it helps to visually understand that Easter involves more steps than Servois. I can change it if you prefer.
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Yeah it also looks more like the other code like this. It's just not what I'm used too seeing, so I'll leave it up to your discretion.
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I agree with you, it also felt strange to me, this algorithm is strange :)
I tried another way, what do you think?
| computus mode year = | ||
| let | ||
| -- Year's position on the 19 year metonic cycle | ||
| a = year `mod` 19 |
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I don't mind going either way here. It looks like this conversation is the only one holding this PR back.
Added the Haskell implementation of the algorithm. It's been a while :)
Super straightforward translation of the Julia code.