diff --git a/benchmark/Streamly/Benchmark/FileSystem/Handle/Read.hs b/benchmark/Streamly/Benchmark/FileSystem/Handle/Read.hs
index 24632777..e5170253 100644
--- a/benchmark/Streamly/Benchmark/FileSystem/Handle/Read.hs
+++ b/benchmark/Streamly/Benchmark/FileSystem/Handle/Read.hs
@@ -33,7 +33,6 @@ import qualified Streamly.Data.Stream as Stream
 import qualified Streamly.Data.Fold as Fold
 import qualified Streamly.FileSystem.Handle as FH
 import qualified Streamly.Internal.Data.Array as A
-import qualified Streamly.Internal.Data.Array as AT
 import qualified Streamly.Internal.Data.Fold as FL
 import qualified Streamly.Internal.Data.Stream as IP
 import qualified Streamly.Internal.FileSystem.Handle as IFH
@@ -48,7 +47,7 @@ import Streamly.Benchmark.Common.Handle
 #ifdef INSPECTION
 import Streamly.Internal.Data.Stream (Step(..), FoldMany)
 
-import qualified Streamly.Internal.Data.MutArray as MA
+import qualified Streamly.Internal.Data.MutArray as MutArray
 import qualified Streamly.Internal.Data.Stream as D
 import qualified Streamly.Internal.Data.Unfold as IUF
 
@@ -69,7 +68,7 @@ readLast = S.fold Fold.last . S.unfold FH.reader
 inspect $ hasNoTypeClasses 'readLast
 inspect $ 'readLast `hasNoType` ''Step -- S.unfold
 inspect $ 'readLast `hasNoType` ''IUF.ConcatState -- FH.read/UF.many
-inspect $ 'readLast `hasNoType` ''MA.ArrayUnsafe  -- FH.read/A.read
+inspect $ 'readLast `hasNoType` ''MutArray.ArrayUnsafe  -- FH.read/A.read
 #endif
 
 -- assert that flattenArrays constructors are not present
@@ -81,7 +80,7 @@ readCountBytes = S.fold Fold.length . S.unfold FH.reader
 inspect $ hasNoTypeClasses 'readCountBytes
 inspect $ 'readCountBytes `hasNoType` ''Step -- S.unfold
 inspect $ 'readCountBytes `hasNoType` ''IUF.ConcatState -- FH.read/UF.many
-inspect $ 'readCountBytes `hasNoType` ''MA.ArrayUnsafe  -- FH.read/A.read
+inspect $ 'readCountBytes `hasNoType` ''MutArray.ArrayUnsafe  -- FH.read/A.read
 #endif
 
 -- | Count the number of lines in a file.
@@ -96,7 +95,7 @@ readCountLines =
 inspect $ hasNoTypeClasses 'readCountLines
 inspect $ 'readCountLines `hasNoType` ''Step
 inspect $ 'readCountLines `hasNoType` ''IUF.ConcatState -- FH.read/UF.many
-inspect $ 'readCountLines `hasNoType` ''MA.ArrayUnsafe  -- FH.read/A.read
+inspect $ 'readCountLines `hasNoType` ''MutArray.ArrayUnsafe  -- FH.read/A.read
 #endif
 
 -- | Count the number of words in a file.
@@ -120,7 +119,7 @@ readSumBytes = S.fold Fold.sum . S.unfold FH.reader
 inspect $ hasNoTypeClasses 'readSumBytes
 inspect $ 'readSumBytes `hasNoType` ''Step
 inspect $ 'readSumBytes `hasNoType` ''IUF.ConcatState -- FH.read/UF.many
-inspect $ 'readSumBytes `hasNoType` ''MA.ArrayUnsafe  -- FH.read/A.read
+inspect $ 'readSumBytes `hasNoType` ''MutArray.ArrayUnsafe  -- FH.read/A.read
 #endif
 
 -- XXX When we mark this with INLINE and we have two benchmarks using S.drain
@@ -236,13 +235,13 @@ groupsOf :: Int -> Handle -> IO Int
 groupsOf n inh =
     -- writeNUnsafe gives 2.5x boost here over writeN.
     S.fold Fold.length
-        $ IP.groupsOf n (AT.writeNUnsafe n) (S.unfold FH.reader inh)
+        $ IP.groupsOf n (A.writeNUnsafe n) (S.unfold FH.reader inh)
 
 #ifdef INSPECTION
 inspect $ hasNoTypeClasses 'groupsOf
 inspect $ 'groupsOf `hasNoType` ''Step
 inspect $ 'groupsOf `hasNoType` ''FoldMany
-inspect $ 'groupsOf `hasNoType` ''AT.ArrayUnsafe -- AT.writeNUnsafe
+inspect $ 'groupsOf `hasNoType` ''MutArray.ArrayUnsafe -- AT.writeNUnsafe
                                                  -- FH.read/A.read
 inspect $ 'groupsOf `hasNoType` ''IUF.ConcatState -- FH.read/UF.many
 #endif
diff --git a/benchmark/Streamly/Benchmark/FileSystem/Handle/ReadWrite.hs b/benchmark/Streamly/Benchmark/FileSystem/Handle/ReadWrite.hs
index a5611e2e..19a1e4fe 100644
--- a/benchmark/Streamly/Benchmark/FileSystem/Handle/ReadWrite.hs
+++ b/benchmark/Streamly/Benchmark/FileSystem/Handle/ReadWrite.hs
@@ -42,8 +42,7 @@ import Streamly.Internal.Data.Stream (Step(..))
 
 import qualified Streamly.Internal.Data.Stream as D
 import qualified Streamly.Internal.Data.Tuple.Strict as Strict
-import qualified Streamly.Internal.Data.MutArray.Stream as MAS
-import qualified Streamly.Internal.Data.Array as AT
+import qualified Streamly.Internal.Data.MutArray as MutArray
 
 import Test.Inspection
 #endif
@@ -83,7 +82,7 @@ copyStream inh outh = S.fold (FH.write outh) (S.unfold FH.reader inh)
 inspect $ hasNoTypeClasses 'copyStream
 inspect $ 'copyStream `hasNoType` ''Step -- S.unfold
 inspect $ 'copyStream `hasNoType` ''IUF.ConcatState -- FH.read/UF.many
-inspect $ 'copyStream `hasNoType` ''AT.ArrayUnsafe -- FH.write/writeNUnsafe
+inspect $ 'copyStream `hasNoType` ''MutArray.ArrayUnsafe -- FH.write/writeNUnsafe
                                                    -- FH.read/A.read
 inspect $ 'copyStream `hasNoType` ''Strict.Tuple3' -- FH.write/chunksOf
 #endif
@@ -109,8 +108,8 @@ readFromBytesNull inh devNull = IFH.putBytes devNull $ S.unfold FH.reader inh
 #ifdef INSPECTION
 inspect $ hasNoTypeClasses 'readFromBytesNull
 inspect $ 'readFromBytesNull `hasNoType` ''Step
-inspect $ 'readFromBytesNull `hasNoType` ''MAS.SpliceState
-inspect $ 'readFromBytesNull `hasNoType` ''AT.ArrayUnsafe -- FH.fromBytes/S.chunksOf
+inspect $ 'readFromBytesNull `hasNoType` ''MutArray.SpliceState
+inspect $ 'readFromBytesNull `hasNoType` ''MutArray.ArrayUnsafe -- FH.fromBytes/S.chunksOf
 inspect $ 'readFromBytesNull `hasNoType` ''D.FoldMany
 #endif
 
@@ -123,8 +122,8 @@ readWithFromBytesNull inh devNull =
 #ifdef INSPECTION
 inspect $ hasNoTypeClasses 'readWithFromBytesNull
 inspect $ 'readWithFromBytesNull `hasNoType` ''Step
-inspect $ 'readWithFromBytesNull `hasNoType` ''MAS.SpliceState
-inspect $ 'readWithFromBytesNull `hasNoType` ''AT.ArrayUnsafe -- FH.fromBytes/S.chunksOf
+inspect $ 'readWithFromBytesNull `hasNoType` ''MutArray.SpliceState
+inspect $ 'readWithFromBytesNull `hasNoType` ''MutArray.ArrayUnsafe -- FH.fromBytes/S.chunksOf
 inspect $ 'readWithFromBytesNull `hasNoType` ''D.FoldMany
 #endif
 
@@ -171,7 +170,7 @@ writeReadWith inh devNull = IUF.fold fld unf (defaultChunkSize, inh)
 inspect $ hasNoTypeClasses 'writeReadWith
 inspect $ 'writeReadWith `hasNoType` ''Step
 inspect $ 'writeReadWith `hasNoType` ''IUF.ConcatState -- FH.read/UF.many
-inspect $ 'writeReadWith `hasNoType` ''AT.ArrayUnsafe -- FH.write/writeNUnsafe
+inspect $ 'writeReadWith `hasNoType` ''MutArray.ArrayUnsafe -- FH.write/writeNUnsafe
                                                       -- FH.read/A.read
 #endif
 
@@ -188,7 +187,7 @@ writeRead inh devNull = IUF.fold fld unf inh
 inspect $ hasNoTypeClasses 'writeRead
 inspect $ 'writeRead `hasNoType` ''Step
 inspect $ 'writeRead `hasNoType` ''IUF.ConcatState -- FH.read/UF.many
-inspect $ 'writeRead `hasNoType` ''AT.ArrayUnsafe -- FH.write/writeNUnsafe
+inspect $ 'writeRead `hasNoType` ''MutArray.ArrayUnsafe -- FH.write/writeNUnsafe
                                                   -- FH.read/A.read
 #endif
 
diff --git a/benchmark/Streamly/Benchmark/Unicode/Stream.hs b/benchmark/Streamly/Benchmark/Unicode/Stream.hs
index 36ae5d9e..4a316fea 100644
--- a/benchmark/Streamly/Benchmark/Unicode/Stream.hs
+++ b/benchmark/Streamly/Benchmark/Unicode/Stream.hs
@@ -45,9 +45,10 @@ import Streamly.Benchmark.Common.Handle
 #ifdef INSPECTION
 import Streamly.Internal.Data.MutByteArray (Unbox)
 import Streamly.Internal.Data.Stream (Step(..))
+import qualified Streamly.Internal.Data.Array as Array
+import qualified Streamly.Internal.Data.MutArray as MutArray
 import qualified Streamly.Internal.Data.Fold as Fold
 import qualified Streamly.Internal.Data.Tuple.Strict as Strict
-import qualified Streamly.Internal.Data.Array as Array
 
 import Test.Inspection
 #endif
@@ -223,7 +224,7 @@ inspect $ 'copyStreamLatin1' `hasNoType` ''Step
 inspect $ 'copyStreamLatin1' `hasNoType` ''Unfold.ConcatState -- Handle.read/UF.many
 
 inspect $ 'copyStreamLatin1' `hasNoType` ''Fold.Step
-inspect $ 'copyStreamLatin1' `hasNoType` ''Array.ArrayUnsafe -- Handle.write/writeNUnsafe
+inspect $ 'copyStreamLatin1' `hasNoType` ''MutArray.ArrayUnsafe -- Handle.write/writeNUnsafe
                                                              -- Handle.read/Array.read
 inspect $ 'copyStreamLatin1' `hasNoType` ''Strict.Tuple3' -- Handle.write/chunksOf
 #endif
@@ -244,7 +245,7 @@ inspect $ 'copyStreamLatin1 `hasNoType` ''Unfold.ConcatState -- Handle.read/UF.m
 
 inspect $ 'copyStreamLatin1 `hasNoType` ''Fold.ManyState
 inspect $ 'copyStreamLatin1 `hasNoType` ''Fold.Step
-inspect $ 'copyStreamLatin1 `hasNoType` ''Array.ArrayUnsafe -- Handle.write/writeNUnsafe
+inspect $ 'copyStreamLatin1 `hasNoType` ''MutArray.ArrayUnsafe -- Handle.write/writeNUnsafe
                                                             -- Handle.read/Array.read
 inspect $ 'copyStreamLatin1 `hasNoType` ''Strict.Tuple3' -- Handle.write/chunksOf
 #endif
diff --git a/core/src/Streamly/Internal/Data/Array/Type.hs b/core/src/Streamly/Internal/Data/Array/Type.hs
index b6ee712a..4f9ff56b 100644
--- a/core/src/Streamly/Internal/Data/Array/Type.hs
+++ b/core/src/Streamly/Internal/Data/Array/Type.hs
@@ -2,7 +2,6 @@
 -- |
 -- Module      : Streamly.Internal.Data.Array.Type
 -- Copyright   : (c) 2020 Composewell Technologies
---
 -- License     : BSD3-3-Clause
 -- Maintainer  : streamly@composewell.com
 -- Stability   : experimental
@@ -10,72 +9,42 @@
 --
 -- See notes in "Streamly.Internal.Data.MutArray.Type"
 --
+
 module Streamly.Internal.Data.Array.Type
     (
     -- ** Type
     -- $arrayNotes
       Array (..)
-    , asPtrUnsafe
-    , nil
 
-    -- ** Freezing and Thawing
+    -- ** Conversion
+    -- *** Mutable and Immutable
     , unsafeFreeze
     , unsafeFreezeWithShrink
     , unsafeThaw
 
-    -- ** Pinning and Unpinning
+    -- *** Pinned and Unpinned
     , pin
     , unpin
     , isPinned
 
+    -- *** Casting
+    , asPtrUnsafe
+
     -- ** Construction
-    , splice
+    , nil
 
-    , fromList
-    , pinnedFromList
-    , fromListN
-    , pinnedFromListN
-    , fromListRev
-    , fromListRevN
-    , fromStreamN
-    , fromStream
-    , fromPureStreamN
-    , fromPureStream
-    , fromByteStr#
-    , fromByteStr
-    , fromPtrN
-    , fromChunksK
-
-    -- ** Split
-    , breakOn
-    , splitAt
-
-    -- ** Cloning arrays
+    -- *** Cloning
+    -- XXX Why would we clone an immutable array?
     , clone
     , pinnedClone
 
-    -- * Unfolds
-    , reader
-    , readerUnsafe
-    , producer -- experimental
+    -- *** Slicing
+    -- | Get a subarray without copying
+    , splitAt
+    , breakOn -- XXX requires MonadIO
 
-    -- ** Elimination
-    , unsafeIndexIO
-    , getIndexUnsafe
-    , byteLength
-    , length
-
-    , foldl'
-    , foldr
-
-    , toStreamK
-    , toStreamKRev
-    , read
-    , readRev
-    , readerRev
-    , toList
-
-    -- ** Folds
+    -- *** Stream Folds
+    , unsafeMakePure
     , writeWith
     , writeN
     , pinnedWriteN
@@ -85,17 +54,75 @@ module Streamly.Internal.Data.Array.Type
     , pinnedWriteNAligned
     , write
     , pinnedWrite
-    , unsafeMakePure
+
+    -- *** From containers
+    , fromListN
+    , pinnedFromListN
+    , fromList
+    , pinnedFromList
+    , fromListRevN
+    , fromListRev
+    , fromStreamN
+    , fromStream
+    , fromPureStreamN
+    , fromPureStream
+    , fromByteStr#
+    , fromByteStr
+    , fromPtrN
+    , fromChunksK
+
+    -- ** Reading
+
+    -- *** Indexing
+    , unsafeIndexIO -- XXX rename to getIndexUnsafeIO
+    , getIndexUnsafe
+
+    -- *** To Streams
+    , read
+    , readRev
+    , toStreamK
+    , toStreamKRev
+
+    -- *** To Containers
+    , toList
+
+    -- *** Unfolds
+    , producer -- experimental
+    , readerUnsafe
+    , reader
+    , readerRev
+
+    -- *** Size
+    , length
+    , byteLength
+
+    -- ** Folding
+    , foldl'
+    , foldr
     , byteCmp
     , byteEq
 
+    -- ** Appending
+    , splice -- XXX requires MonadIO
+
     -- ** Streams of arrays
+    -- *** Chunk
+    -- | Group a stream into arrays.
     , chunksOf
     , pinnedChunksOf
     , buildChunks
+
+    -- *** Split
+    -- | Split an array into slices.
+
+    -- *** Concat
+    -- | Append the arrays in a stream to form a stream of elements.
     , concatChunks
     , concatChunksRev
 
+    -- *** Compact
+    -- | Append the arrays in a stream to form a stream of larger arrays.
+
     -- ** Deprecated
     , unsafeIndex
     , bufferChunks
diff --git a/core/src/Streamly/Internal/Data/MutArray/Type.hs b/core/src/Streamly/Internal/Data/MutArray/Type.hs
index 939c1a2f..64c8d16b 100644
--- a/core/src/Streamly/Internal/Data/MutArray/Type.hs
+++ b/core/src/Streamly/Internal/Data/MutArray/Type.hs
@@ -31,33 +31,44 @@ module Streamly.Internal.Data.MutArray.Type
     -- ** Type
     -- $arrayNotes
       MutArray (..)
+
+    -- ** Conversion
+    -- *** Pinned and Unpinned
     , pin
     , unpin
     , isPinned
 
-    -- -- * Constructing and Writing
+    -- ** Casting
+    , cast
+    , castUnsafe
+    , asBytes
+    , asPtrUnsafe
+    , asUnpinnedPtrUnsafe
+
     -- ** Construction
     , nil
 
-    -- *** Uninitialized Arrays
+    -- *** New
+    -- | New arrays are always empty arrays with some reserve capacity to
+    -- extend the length without reallocating.
+    , new
+    , newArrayWith
     , pinnedNew
     , pinnedNewBytes
     , pinnedNewAligned
-    , new
-    , newArrayWith
 
-    -- ** Cloning arrays
+    -- *** Cloning
     , clone
     , pinnedClone
 
-    -- ** Slicing
+    -- *** Slicing
     -- | Get a subarray without copying
     , getSliceUnsafe
     , getSlice
     , splitAt -- XXX should be able to express using getSlice
     , breakOn
 
-    -- *** From streams
+    -- *** Stream Folds
     , ArrayUnsafe (..)
     , writeNWithUnsafe
     , writeNWith
@@ -107,10 +118,77 @@ module Streamly.Internal.Data.MutArray.Type
     , swapIndices
     , unsafeSwapIndices
 
+    -- ** Reading
+
+    -- *** Indexing
+    , getIndex
+    , getIndexUnsafe
+    , getIndices -- XXX indexReader
+    , getIndicesWith -- XXX indexReaderWith
+    -- , getFromThenTo
+    , getIndexRev
+
+    -- *** To Streams
+    , read
+    , readRev
+    , toStreamWith
+    , toStreamRevWith
+    , toStreamK
+    , toStreamKWith
+    , toStreamKRev
+    , toStreamKRevWith
+
+    -- *** To Containers
+    , toList
+
+    -- *** Unfolds
+    -- experimental
+    , producerWith
+    , producer
+
+    , reader
+    , readerRevWith
+    , readerRev
+
+    -- ** Size and Capacity
+    -- *** Size
+    , length
+    , byteLength
+
+    -- *** Capacity
+    -- , capacity
+    , byteCapacity
+    , bytesFree
+
+    -- *** Capacity Management
+    , blockSize
+    , arrayChunkBytes
+    , allocBytesToElemCount
+    , realloc
+    , resize
+    , resizeExp
+    , rightSize
+
+    -- ** Folding
+    , foldl'
+    , foldr
+    , byteCmp
+    , byteEq
+
+    -- ** In-place Mutation Algorithms
+    , strip
+    , reverse
+    , permute
+    , partitionBy
+    , shuffleBy
+    , divideBy
+    , mergeBy
+    , bubble
+
     -- ** Growing and Shrinking
-    -- | Arrays grow only at the end, though it is possible to grow on both sides
-    -- and therefore have a cons as well as snoc. But that will require two
-    -- bounds in the array representation.
+    -- | Arrays grow only at the end, though it is possible to grow on both
+    -- sides and therefore have a cons as well as snoc. But that will require
+    -- both lower and upper bound in the array representation.
 
     -- *** Appending elements
     , snocWith
@@ -135,97 +213,32 @@ module Streamly.Internal.Data.MutArray.Type
     -- , appendSlice
     -- , appendSliceFrom
 
-    -- ** Eliminating and Reading
-
-    -- *** To streams
-    , reader
-    , readerRevWith
-    , readerRev
-
-    -- *** To containers
-    , toStreamWith
-    , toStreamRevWith
-    , toStreamKWith
-    , toStreamKRevWith
-    , read
-    , readRev
-    , toStreamK
-    , toStreamKRev
-    , toList
-
-    -- experimental
-    , producerWith
-    , producer
-
-    -- *** Random reads
-    , getIndex
-    , getIndexUnsafe
-    , getIndices
-    , getIndicesWith
-    -- , getFromThenTo
-    , getIndexRev
-
-    -- ** Memory Management
-    , blockSize
-    , arrayChunkBytes
-    , allocBytesToElemCount
-    , realloc
-    , resize
-    , resizeExp
-    , rightSize
-
-    -- ** Size
-    , length
-    , byteLength
-    -- , capacity
-    , byteCapacity
-    , bytesFree
-
-    -- ** In-place Mutation Algorithms
-    , strip
-    , reverse
-    , permute
-    , partitionBy
-    , shuffleBy
-    , divideBy
-    , mergeBy
-    , bubble
-
-    -- ** Casting
-    , cast
-    , castUnsafe
-    , asBytes
-    , asPtrUnsafe
-    , asUnpinnedPtrUnsafe
-
-    -- ** Folding
-    , foldl'
-    , foldr
-    , cmp
-    , byteCmp
-    , byteEq
-
     -- Arrays of arrays
     --  We can add dimensionality parameter to the array type to get
     --  multidimensional arrays. Multidimensional arrays would just be a
     --  convenience wrapper on top of single dimensional arrays.
 
     -- ** Streams of Arrays
-    -- *** Group a stream into arrays
+    -- *** Chunk
+    -- | Group a stream into arrays.
     , chunksOf
     , pinnedChunksOf
     , buildChunks
 
-    -- *** Split an array into slices
+    -- *** Split
+    -- | Split an array into slices.
+
     -- , getSlicesFromLenN
     , splitOn
     -- , slicesOf
 
-    -- *** Flatten a stream of arrays
+    -- *** Concat
+    -- | Append the arrays in a stream to form a stream of elements.
     , concatChunks
     , concatChunksRev
 
-    -- *** Compaction
+    -- *** Compact
+    -- | Append the arrays in a stream to form a stream of larger arrays.
     , SpliceState (..)
     , pCompactChunksLE
     , rCompactChunksLE
@@ -247,6 +260,7 @@ module Streamly.Internal.Data.MutArray.Type
     , fromArrayStreamK
     , fromStreamDN
     , fromStreamD
+    , cmp
     )
 where