From de9f1a16b1ff1515f7cad26ff14add59283263dc Mon Sep 17 00:00:00 2001
From: Ellis Kesterton <erk4@st-andrews.ac.uk>
Date: Wed, 3 Jan 2024 20:43:01 +0000
Subject: [PATCH 1/2] Implement "mapSplitter"

---
 src/Data/List/Split.hs           |  1 +
 src/Data/List/Split/Internals.hs | 13 +++++++++++++
 2 files changed, 14 insertions(+)

diff --git a/src/Data/List/Split.hs b/src/Data/List/Split.hs
index 1a12f99..46951a0 100644
--- a/src/Data/List/Split.hs
+++ b/src/Data/List/Split.hs
@@ -61,6 +61,7 @@ module Data.List.Split (
   dropInitBlank,
   dropFinalBlank,
   dropInnerBlanks,
+  mapSplitter,
 
   -- ** Derived combinators
   -- $derived
diff --git a/src/Data/List/Split/Internals.hs b/src/Data/List/Split/Internals.hs
index d982137..0b71670 100644
--- a/src/Data/List/Split/Internals.hs
+++ b/src/Data/List/Split/Internals.hs
@@ -379,6 +379,19 @@ dropFinalBlank s = s {finalBlankPolicy = DropBlank}
 dropInnerBlanks :: Splitter a -> Splitter a
 dropInnerBlanks s = s {condensePolicy = DropBlankFields}
 
+-- | Split over a different type of element by performing a preprocessing step.
+--
+-- >>> split (mapSplitter snd $ oneOf "-_") $ zip [0..] "a-bc_d"
+-- [[(0,'a')],[(1,'-')],[(2,'b'),(3,'c')],[(4,'_')],[(5,'d')]]
+--
+-- >>> split (mapSplitter toLower $ dropDelims $ whenElt (== 'x')) "abXcxd"
+-- ["ab","c","d"]
+mapSplitter :: (b -> a) -> Splitter a -> Splitter b
+mapSplitter f (Splitter d dp cp ibp fbp) = Splitter (mapDelimiter f d) dp cp ibp fbp
+ where
+  mapDelimiter :: (b -> a) -> Delimiter a -> Delimiter b
+  mapDelimiter g (Delimiter xs) = Delimiter $ map (. g) xs
+
 -- ** Derived combinators
 
 -- | Drop all blank chunks from the output, and condense consecutive

From f7bc600f3477bb092fa67cff8ee5388b3cf1bb1e Mon Sep 17 00:00:00 2001
From: Ellis Kesterton <31514698+eayus@users.noreply.github.com>
Date: Sun, 7 Jan 2024 17:10:54 +0000
Subject: [PATCH 2/2] Fix doctest imports

---
 src/Data/List/Split/Internals.hs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/src/Data/List/Split/Internals.hs b/src/Data/List/Split/Internals.hs
index 0b71670..03c3431 100644
--- a/src/Data/List/Split/Internals.hs
+++ b/src/Data/List/Split/Internals.hs
@@ -384,6 +384,7 @@ dropInnerBlanks s = s {condensePolicy = DropBlankFields}
 -- >>> split (mapSplitter snd $ oneOf "-_") $ zip [0..] "a-bc_d"
 -- [[(0,'a')],[(1,'-')],[(2,'b'),(3,'c')],[(4,'_')],[(5,'d')]]
 --
+-- >>> import Data.Char (toLower)
 -- >>> split (mapSplitter toLower $ dropDelims $ whenElt (== 'x')) "abXcxd"
 -- ["ab","c","d"]
 mapSplitter :: (b -> a) -> Splitter a -> Splitter b