#PatternSynonyms - Twitter Hashtag

about 5 years ago

#PatternSynonyms: Is there a way to define a pattern that when given a type application only matches a TypeRep of that type? f :: TypeRep a -> a f (Is @Int) = 10 f (Is @[] `App` Is @Int) = [1,2,3,4]

Iceland_jack's tweet photo. #PatternSynonyms: Is there a way to define a pattern that when given a type application only matches a TypeRep of that type?

f :: TypeRep a -> a
f (Is @Int) = 10
f (Is @[] `App` Is @Int) = [1,2,3,4] https://t.co/KoEpP3edkb

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Dad×3_jack @Iceland_jack

almost 6 years ago

@ijks_w So for lenses, we have 'is' and 'isn'\''t' operators but I agree that there are many places in Haskell where patterns feel, how to say, not just not first-class but underdeveloped or unintegrated into the rest of the language. #PatternSynonyms was a big step forward but

$Iceland_jack's tweet photo. @ijks_w So for lenses, we have 'is' and 'isn'\''t' operators but I agree that there are many places in Haskell where patterns feel, how to say, not just not first-class but underdeveloped or unintegrated into the rest of the language. #PatternSynonyms was a big step forward but https://t.co/ls6SIbA4t6$

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Dad×3_jack @Iceland_jack

about 6 years ago

@DaTwinkDaddy I'm susprised how long #PatternSynonyms took, we haven't "solved" coverage at all and it feels like people are oddly disinterested. There are several low-hanging fruits

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Dad×3_jack @Iceland_jack

about 6 years ago

1. Was GHC first to introduce deriving clauses? 2. Why has adoption taken so long? Rust, PureScript both have them, now Scala, but what other? 3. Lack of type classes? 4. I have a similar question about patterns and #PatternSynonyms!

Igal Tabachnik

@hmemcpy

about 6 years ago

Typeclass derivation is coming to Scala 3 - great talk by @cbirchall at #SignifyScalaConf

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Dad×3_jack @Iceland_jack

over 6 years ago

@_osa1 Yes and patterns have always got second-class attention in Haskell given how late #PatternSynonyms appeared (before, abstracting patterns was impossible) in its history with a lousy story for complete patterns; can't be parameterised ..

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Dad×3_jack @Iceland_jack

over 6 years ago

A little less next time #PatternSynonyms

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Dad×3_jack @Iceland_jack

over 6 years ago

@lotz84_ :3 #PatternSynonyms

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Dad×3_jack @Iceland_jack

over 6 years ago

How realistically can we make Data.Functor.{Sum,Product} f g a into newtypes over (f a, g a) and (f a `Either` g a) with #PatternSynonyms pattern Pair as bs = Product__ (as, bs) pattern InL as = Sum__ (Left as) pattern InR bs = Sum__ (Right bs)

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Dad×3_jack @Iceland_jack

almost 7 years ago

#PatternSynonyms #ImplicitParams

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Dad×3_jack @Iceland_jack

almost 7 years ago

PatternSynonyms for expressive code by Raghu Kaippully @rkaippully https://t.co/gA9BaMdqq4 #PatternSynonyms

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Dad×3_jack @Iceland_jack

almost 7 years ago

Bidirectional #PatternSynonyms

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Dad×3_jack @Iceland_jack

about 7 years ago

@chrislpenner At that point why not define a new type or #PatternSynonyms pattern Retry = True

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Dad×3_jack @Iceland_jack

about 7 years ago

#PatternSynonyms + #ViewPatterns #GHCTrac #Trac12001 https://t.co/SouDEjWGYD

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Dad×3_jack @Iceland_jack

about 7 years ago

#PatternSynonyms sometimes are rather much

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Dad×3_jack @Iceland_jack

over 7 years ago

Good example to teach #PatternSynonyms {-# Language PatternSynonyms #-} pattern LessThan :: Ordering pattern LessThan = LT pattern EqualTo :: Ordering pattern EqualTo = EQ pattern GreaterThan :: Ordering pattern GrearerThan = GT

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Dad×3_jack @Iceland_jack

over 7 years ago

We can give a nickname to lists, to be consistent with other names type List = [] and now we define #PatternSynonyms for [] :: List a (:) :: a -> List a -> List a

Iceland_jack's tweet photo. We can give a nickname to lists, to be consistent with other names

type List = []

and now we define #PatternSynonyms for

[] :: List a
(:) :: a -> List a -> List a https://t.co/ot5J0w83Ft

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Dad×3_jack @Iceland_jack

over 7 years ago

We can also write #PatternSynonyms for 0 pattern Zero :: (Eq a, Num a) => a pattern Zero = 0 For pattern synonyms, this is NOT equivalent pattern Zero :: Eq a => Num a => a

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