From a4f3e112954e1b785c84c339bcbd83597a89335e Mon Sep 17 00:00:00 2001
From: Joey Hess <joeyh@debian.org>
Date: Tue, 3 Dec 2013 15:02:21 -0400
Subject: git-repair (1.20131203) unstable; urgency=low

  * Fix build deps. Closes: #731179

# imported from the archive
---
 Utility/PartialPrelude.hs | 68 +++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 68 insertions(+)
 create mode 100644 Utility/PartialPrelude.hs

(limited to 'Utility/PartialPrelude.hs')

diff --git a/Utility/PartialPrelude.hs b/Utility/PartialPrelude.hs
new file mode 100644
index 0000000..6efa093
--- /dev/null
+++ b/Utility/PartialPrelude.hs
@@ -0,0 +1,68 @@
+{- Parts of the Prelude are partial functions, which are a common source of
+ - bugs.
+ -
+ - This exports functions that conflict with the prelude, which avoids
+ - them being accidentially used.
+ -}
+
+module Utility.PartialPrelude where
+
+import qualified Data.Maybe
+
+{- read should be avoided, as it throws an error
+ - Instead, use: readish -}
+read :: Read a => String -> a
+read = Prelude.read
+
+{- head is a partial function; head [] is an error
+ - Instead, use: take 1 or headMaybe -}
+head :: [a] -> a
+head = Prelude.head
+
+{- tail is also partial
+ - Instead, use: drop 1 -}
+tail :: [a] -> [a]
+tail = Prelude.tail
+
+{- init too
+ - Instead, use: beginning -}
+init :: [a] -> [a]
+init = Prelude.init
+
+{- last too
+ - Instead, use: end or lastMaybe -}
+last :: [a] -> a
+last = Prelude.last
+
+{- Attempts to read a value from a String.
+ -
+ - Ignores leading/trailing whitespace, and throws away any trailing
+ - text after the part that can be read.
+ -
+ - readMaybe is available in Text.Read in new versions of GHC,
+ - but that one requires the entire string to be consumed.
+ -}
+readish :: Read a => String -> Maybe a
+readish s = case reads s of
+	((x,_):_) -> Just x
+	_ -> Nothing
+
+{- Like head but Nothing on empty list. -}
+headMaybe :: [a] -> Maybe a
+headMaybe = Data.Maybe.listToMaybe
+
+{- Like last but Nothing on empty list. -}
+lastMaybe :: [a] -> Maybe a
+lastMaybe [] = Nothing
+lastMaybe v = Just $ Prelude.last v
+
+{- All but the last element of a list.
+ - (Like init, but no error on an empty list.) -}
+beginning :: [a] -> [a]
+beginning [] = []
+beginning l = Prelude.init l
+
+{- Like last, but no error on an empty list. -}
+end :: [a] -> [a]
+end [] = []
+end l = [Prelude.last l]
-- 
cgit v1.2.3