49 lines
1.5 KiB
Haskell
49 lines
1.5 KiB
Haskell
{-
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Copyright 2022 Vidar Holen
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This file is part of ShellCheck.
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https://www.shellcheck.net
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ShellCheck is free software: you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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ShellCheck is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <https://www.gnu.org/licenses/>.
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-}
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-- Generic basic utility functions
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module ShellCheck.Prelude where
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-- Get element 0 or a default. Like `head` but safe.
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headOrDefault _ (a:_) = a
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headOrDefault def _ = def
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-- Get the last element or a default. Like `last` but safe.
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lastOrDefault def [] = def
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lastOrDefault _ list = last list
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--- Get element n of a list, or Nothing. Like `!!` but safe.
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(!!!) list i =
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case drop i list of
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[] -> Nothing
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(r:_) -> Just r
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-- Like mconcat but for Semigroups
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sconcat1 :: (Semigroup t) => [t] -> t
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sconcat1 [x] = x
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sconcat1 (x:xs) = x <> sconcat1 xs
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sconcatOrDefault def [] = def
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sconcatOrDefault _ list = sconcat1 list
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-- For more actionable "impossible" errors
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pleaseReport str = "ShellCheck internal error, please report: " ++ str
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