52 lines
1.5 KiB
Haskell
52 lines
1.5 KiB
Haskell
{- This file is part of Vervis.
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-
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- Written in 2016 by fr33domlover <fr33domlover@riseup.net>.
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-
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- ♡ Copying is an act of love. Please copy, reuse and share.
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-
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- The author(s) have dedicated all copyright and related and neighboring
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- rights to this software to the public domain worldwide. This software is
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- distributed without any warranty.
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-
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- You should have received a copy of the CC0 Public Domain Dedication along
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- with this software. If not, see
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- <http://creativecommons.org/publicdomain/zero/1.0/>.
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-}
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module Control.Applicative.Local
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( atMost
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, atMost_
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, upTo
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, upTo_
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)
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where
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import Prelude
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import Control.Applicative
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-- | Apply action between zero and @n@ times, inclusive, and list the results.
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atMost :: Alternative f => Int -> f a -> f [a]
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atMost n action = go n
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where
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go n =
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if n <= 0
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then pure []
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else liftA2 (:) action (go $ n - 1) <|> pure []
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-- | Apply action between zero and @n@ times, inclusive, and discard results.
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atMost_ :: Alternative f => Int -> f a -> f ()
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atMost_ n action = go n
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where
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go n =
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if n <= 0
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then pure ()
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else action *> (go $ n - 1) <|> pure ()
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-- | Apply action between one and @n@ times, inclusive, and list the results.
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upTo :: Alternative f => Int -> f a -> f [a]
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upTo n action = liftA2 (:) action $ atMost n action
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-- | Apply action between one and @n@ times, inclusive, and discard results.
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upTo_ :: Alternative f => Int -> f a -> f ()
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upTo_ n action = action *> atMost_ n action
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