31 lines
963 B
Haskell
31 lines
963 B
Haskell
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{- 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 Data.List.Local
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( -- groupByFst
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)
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where
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import Prelude
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-- | Takes a list of pairs and groups them by consecutive ranges with equal
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-- first element. Returns a list of pairs, where each pair corresponds to one
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-- such range.
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groupByFst :: Eq a => [(a, b)] -> [(a, [b])]
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groupByFst [] = []
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groupByFst ((x, y):ps) =
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let (same, rest) = span ((== x) . fst) ps
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in (x, y : map snd same) : groupByFst rest
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