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plurals

PO
primarykey
Id
11917157
data
AcceptedAnswerId
0
AnswerCount
0
ClosedDate
CommentCount
0
CommunityOwnedDate
CreationDate
2012-08-11T19:51:31.417
FavoriteCount
0
LastActivityDate
2012-08-12T23:38:08.563
LastEditDate
2012-08-12T23:38:08.563
LastEditorUserId
849891
OwnerUserId
849891
ParentId
11906347
PostTypeId
2
Score
2
ViewCount
0
LastEditorDisplayName
text
Body
It might be easier to use combinators, e.g. <code>_S</code> and <code>_K</code>, symbolically, and not their definitions as lambda-expressions, <pre><code>_S f g x = f x (g x) _K x y = x </code></pre> With functions, <code>fmap</code> is <code>(.)</code> and <code><*></code> is <code>_S</code>, as others already mentioned. So, <pre><code>sequenceA [(+3),(+2)] 3 == ( ((:) <$> (+3)) <*> sequenceA [(+2)] ) 3 == _S ((:).(+3)) ( ((:) <$> (+2)) <*> pure [] ) 3 == _S ((:).(+3)) ( _S ((:).(+2)) (_K []) ) 3 == ((:).(+3)) 3 ( _S ((:).(+2)) (_K []) 3 ) == ((:).(+3)) 3 ( ((:).(+2)) 3 (_K [] 3) ) == (6:) ( (5:) [] ) == [6,5] </code></pre> So it might be easier to decompose expressions down to basic functions and combinators and stop there (i.e. not decomposing them to their lambda expressions), using their "re-write rules" in manipulating the expression to find its more comprehensible form. If you wanted to, you could now write down for yourself a more abstract, informal re-write rule for <code>sequenceA</code> as <pre><code>sequenceA [f,g,..., z] == _S ((:).f) . _S ((:).g) . _S ..... . _S ((:).z) . _K [] </code></pre> and so <pre><code>sequenceA [f,g,..., z] a == ((:).f) a $ ((:).g) a $ ..... $ ((:).z) a $ _K [] a == (f a:) $ (g a:) $ ..... $ (z a:) $ [] == [f a, g a, ..., z a] </code></pre> and hence <pre><code>sequenceA fs a == map ($ a) fs == flip (map . flip ($)) fs a </code></pre> to wit, <pre><code>Prelude Control.Applicative> flip (map . flip ($)) [(+3),(+2)] 3 [6,5] </code></pre>
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1. This table or related slice is empty.
PostParentId
1. POapplicative rewrite (Haskell)
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PostTypePostTypeId
1. PTAnswer
UserLastEditorUserId
1. USWill Ness
UserOwnerUserId
1. USWill Ness
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VotesPostIdCreationDate
1. VO
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2. VO
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