diff --git a/CHANGELOG.md b/CHANGELOG.md
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--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,11 @@
+# Changelog for `try-tools-yj`
+
+All notable changes to this project will be documented in this file.
+
+The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
+and this project adheres to the
+[Haskell Package Versioning Policy](https://pvp.haskell.org/).
+
+## Unreleased
+
+## 0.1.0.0 - YYYY-MM-DD
diff --git a/LICENSE b/LICENSE
new file mode 100644
--- /dev/null
+++ b/LICENSE
@@ -0,0 +1,30 @@
+Copyright Yoshikuni Jujo (c) 2023
+
+All rights reserved.
+
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+    * Redistributions of source code must retain the above copyright
+      notice, this list of conditions and the following disclaimer.
+
+    * Redistributions in binary form must reproduce the above
+      copyright notice, this list of conditions and the following
+      disclaimer in the documentation and/or other materials provided
+      with the distribution.
+
+    * Neither the name of Yoshikuni Jujo nor the names of other
+      contributors may be used to endorse or promote products derived
+      from this software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+"AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
diff --git a/README.md b/README.md
new file mode 100644
--- /dev/null
+++ b/README.md
@@ -0,0 +1,1 @@
+# tools-yj
diff --git a/Setup.hs b/Setup.hs
new file mode 100644
--- /dev/null
+++ b/Setup.hs
@@ -0,0 +1,2 @@
+import Distribution.Simple
+main = defaultMain
diff --git a/src/Control/Concurrent/STM/ToolsYj.hs b/src/Control/Concurrent/STM/ToolsYj.hs
new file mode 100644
--- /dev/null
+++ b/src/Control/Concurrent/STM/ToolsYj.hs
@@ -0,0 +1,16 @@
+{-# OPTIONS_GHC -Wall -fno-warn-tabs #-}
+
+module Control.Concurrent.STM.ToolsYj (newDefaultTVar, readModifyTVar, checkFlag) where
+
+import Control.Concurrent.STM
+import Data.Default
+import Data.Bool
+
+newDefaultTVar :: Default a => STM (TVar a)
+newDefaultTVar = newTVar def
+
+readModifyTVar :: TVar a -> (a -> a) -> STM a
+readModifyTVar v f = readTVar v <* modifyTVar v f
+
+checkFlag :: TVar Bool -> STM Bool
+checkFlag flg = readTVar flg >>= bool (pure False) (True <$ writeTVar flg False)
diff --git a/src/Data/Bits/ToolsYj.hs b/src/Data/Bits/ToolsYj.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Bits/ToolsYj.hs
@@ -0,0 +1,8 @@
+{-# OPTIONS_GHC -Wall -fno-warn-tabs #-}
+
+module Data.Bits.ToolsYj (checkBits) where
+
+import Data.Bits
+
+checkBits :: Bits bs => bs -> bs -> Bool
+checkBits wnt = (== wnt) . (.&. wnt)
diff --git a/src/Data/Bool/ToolsYj.hs b/src/Data/Bool/ToolsYj.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Bool/ToolsYj.hs
@@ -0,0 +1,14 @@
+{-# OPTIONS_GHC -Wall -fno-warn-tabs #-}
+
+module Data.Bool.ToolsYj (onlyIf, errorIf, errorIfNot) where
+
+import Data.Bool
+
+onlyIf :: (a -> Bool) -> a -> Maybe a
+onlyIf p x = bool Nothing (Just x) (p x)
+
+errorIf :: String -> Bool -> IO ()
+errorIf msg = bool (pure ()) (error msg)
+
+errorIfNot :: String -> Bool -> IO ()
+errorIfNot msg = bool (error msg) (pure ())
diff --git a/src/Data/Either/ToolsYj.hs b/src/Data/Either/ToolsYj.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Either/ToolsYj.hs
@@ -0,0 +1,12 @@
+{-# LANGUAGE LambdaCase #-}
+{-# OPTIONS_GHC -Wall -fno-warn-tabs #-}
+
+module Data.Either.ToolsYj (forceRight, forceRight') where
+
+import Control.Exception
+
+forceRight :: Exception e => Either e a -> a
+forceRight = \case Left e -> throw e; Right x -> x
+
+forceRight' :: Either String a -> a
+forceRight' = forceRight . either (Left . ErrorCall) Right
diff --git a/src/Data/Function/ToolsYj.hs b/src/Data/Function/ToolsYj.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Function/ToolsYj.hs
@@ -0,0 +1,15 @@
+{-# OPTIONS_GHC -Wall -fno-warn-tabs #-}
+
+module Data.Function.ToolsYj (const2, const3, const4, const5) where
+
+const2 :: a -> b -> c -> a
+const2 = const . const
+
+const3 :: a -> b -> c -> d -> a
+const3 = const . const2
+
+const4 :: a -> b -> c -> d -> e -> a
+const4 = const . const3
+
+const5 :: a -> b -> c -> d -> e -> f -> a
+const5 = const . const4
diff --git a/src/Data/IORef/ToolsYj.hs b/src/Data/IORef/ToolsYj.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/IORef/ToolsYj.hs
@@ -0,0 +1,18 @@
+{-# LANGUAGE ImportQualifiedPost #-}
+{-# LANGUAGE TupleSections #-}
+{-# LANGUAGE DataKinds, PolyKinds #-}
+{-# LANGUAGE KindSignatures #-}
+{-# OPTIONS_GHC -Wall -fno-warn-tabs #-}
+
+module Data.IORef.ToolsYj (newDefaultIORef, checkFlag) where
+
+import Data.Default
+import Data.Bool
+import Data.IORef
+
+newDefaultIORef :: Default a => IO (IORef a)
+newDefaultIORef = newIORef def
+
+checkFlag :: IORef Bool -> IO Bool
+checkFlag flg =
+	readIORef flg >>= bool (pure False) (True <$ writeIORef flg False)
diff --git a/src/Data/List/ToolsYj.hs b/src/Data/List/ToolsYj.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/List/ToolsYj.hs
@@ -0,0 +1,38 @@
+{-# LANGUAGE LambdaCase #-}
+{-# OPTIONS_GHC -Wall -fno-warn-tabs #-}
+
+module Data.List.ToolsYj (
+	list, list', replicateWithI, replicateMWithI,
+	elemAll, elemNotAll, findDefault, listToTuple4
+	) where
+
+import Data.Maybe
+import Data.List ((\\), find)
+import Data.List.NonEmpty (NonEmpty(..))
+
+list :: b -> (a -> [a] -> b) -> [a] -> b
+list n c = \case [] -> n; x : xs -> c x xs
+
+list' :: b -> (NonEmpty a -> b) -> [a] -> b
+list' n c = \case [] -> n; x : xs -> c $ x :| xs
+
+replicateWithI :: Int -> (Int -> a) -> [a]
+replicateWithI n f = go 0
+	where go i | i < n = f i : go (i + 1) | otherwise = []
+
+replicateMWithI :: Applicative m => Int -> (Int -> m a) -> m [a]
+replicateMWithI n f = go 0
+	where go i | i < n = (:) <$> f i <*> go (i + 1) | otherwise = pure []
+
+elemAll :: Eq a => [a] -> [a] -> Bool
+elemAll es = null . (es \\)
+
+elemNotAll :: Eq a => [a] -> [a] -> Bool
+elemNotAll es = not . elemAll es
+
+findDefault :: a -> (a -> Bool) -> [a] -> a
+findDefault d p = fromMaybe d . find p
+
+listToTuple4 :: [a] -> (a, a, a, a)
+listToTuple4 [r, g, b, a] = (r, g, b, a)
+listToTuple4 _ = error "The length of the list is not 4"
diff --git a/src/Data/Maybe/ToolsYj.hs b/src/Data/Maybe/ToolsYj.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Maybe/ToolsYj.hs
@@ -0,0 +1,28 @@
+{-# LANGUAGE BlockArguments, LambdaCase #-}
+{-# OPTIONS_GHC -Wall -fno-warn-tabs #-}
+
+module Data.Maybe.ToolsYj (
+	forceJust, forceJust', orErrorIO, findMaybe, findMaybeM ) where
+
+import Control.Exception
+
+forceJust :: Exception e => e -> Maybe a -> a
+forceJust e = maybe (throw e) id
+
+forceJust' :: String -> Maybe a -> a
+forceJust' = forceJust . ErrorCall
+
+orErrorIO :: String -> Maybe a -> IO a
+orErrorIO msg = maybe (error msg) pure
+
+findMaybe :: (a -> Maybe b) -> [a] -> Maybe (a, b)
+findMaybe prd = \case
+	[] -> Nothing
+	p : ps -> ($ prd p) \case
+		Nothing -> findMaybe prd ps; Just x -> Just (p, x)
+
+findMaybeM :: Monad m => (a -> m (Maybe b)) -> [a] -> m (Maybe (a, b))
+findMaybeM prd = \case
+	[] -> pure Nothing
+	p : ps -> prd p >>= \case
+		Nothing -> findMaybeM prd ps; Just x -> pure $ Just (p, x)
diff --git a/src/Data/Ord/ToolsYj.hs b/src/Data/Ord/ToolsYj.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Ord/ToolsYj.hs
@@ -0,0 +1,8 @@
+{-# OPTIONS_GHC -Wall -fno-warn-tabs #-}
+
+module Data.Ord.ToolsYj (clamp, Min, Max) where
+
+clamp :: Ord a => Min a -> Max a -> a -> a
+clamp mn mx x | x < mn = mn | x < mx = x | otherwise = mx
+
+type Min a = a; type Max a = a
diff --git a/src/Data/Sequences/ToolsYj.hs b/src/Data/Sequences/ToolsYj.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Sequences/ToolsYj.hs
@@ -0,0 +1,27 @@
+{-# LANGUAGE ImportQualifiedPost #-}
+{-# LANGUAGE TypeOperators #-}
+{-# LANGUAGE FlexibleContexts #-}
+{-# LANGUAGE ViewPatterns #-}
+{-# OPTIONS_GHC -Wall -fno-warn-tabs #-}
+
+module Data.Sequences.ToolsYj (indexing) where
+
+import Data.MonoTraversable qualified as Mono
+import Data.Sequences qualified as Seq
+import Data.Map qualified as M
+
+indexing :: (
+	Mono.MonoFoldable seq, Mono.Element seq ~ Mono.Element seq',
+	Seq.IsSequence seq', Ord (Mono.Element seq),
+	Seq.IsSequence seqi, Enum (Mono.Element seqi) ) => seq -> (seq', seqi)
+indexing (Mono.otoList -> xs) = let
+	(xs', is) = indexingGo 0 M.empty xs in
+	(Seq.fromList $ M.elems xs', Seq.fromList $ toEnum <$> is)
+
+indexingGo :: Ord a => Int -> M.Map a Int -> [a] -> (M.Map Int a, [Int])
+indexingGo _ _ [] = (M.empty, [])
+indexingGo idx rvdct (x : xs) = case M.lookup x rvdct of
+	Nothing -> let
+		(dct, is) = indexingGo (idx + 1) (M.insert x idx rvdct) xs in
+		(M.insert idx x dct, idx : is)
+	Just i -> let (dct, is) = indexingGo idx rvdct xs in (dct, i : is)
diff --git a/src/Data/Text/ToolsYj.hs b/src/Data/Text/ToolsYj.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Text/ToolsYj.hs
@@ -0,0 +1,26 @@
+{-# LANGUAGE ImportQualifiedPost #-}
+{-# LANGUAGE TupleSections #-}
+{-# LANGUAGE DataKinds, PolyKinds #-}
+{-# LANGUAGE KindSignatures #-}
+{-# OPTIONS_GHC -Wall -fno-warn-tabs #-}
+
+module Data.Text.ToolsYj (cstrToText) where
+
+import Foreign.Ptr
+import Foreign.Storable
+import Foreign.C.String
+import Data.Text qualified as Txt
+import Data.Text.Foreign qualified as Txt
+
+cstrToText :: CString -> IO Txt.Text
+cstrToText cs = Txt.peekCStringLen =<< cstringToCStringLen cs
+
+cstringLength :: CString -> IO Int
+cstringLength pc = do
+	c <- peek pc
+	case c of
+		0 -> pure 0
+		_ -> (+ 1) <$> cstringLength (pc `plusPtr` 1)
+
+cstringToCStringLen :: CString -> IO CStringLen
+cstringToCStringLen cs = (cs ,) <$> cstringLength cs
diff --git a/src/Data/Tuple/ToolsYj.hs b/src/Data/Tuple/ToolsYj.hs
new file mode 100644
--- /dev/null
+++ b/src/Data/Tuple/ToolsYj.hs
@@ -0,0 +1,31 @@
+{-# OPTIONS_GHC -Wall -fno-warn-tabs #-}
+
+module Data.Tuple.ToolsYj (
+	uncurryDup,
+	mapTup3, appTup3, mapTup3M, appTup3M, mapTup3M_, appTup3M_
+	) where
+
+import Control.Monad
+
+uncurryDup :: (a -> b -> c -> d) -> ((a, b), c) -> d
+uncurryDup = uncurry . uncurry
+
+mapTup3 :: (a -> b) -> (a, a, a) -> (b, b, b)
+mapTup3 f = appTup3 f f f
+
+appTup3 :: (a -> b) -> (c -> d) -> (e -> f) -> (a, c, e) -> (b, d, f)
+appTup3 f g h (x, y, z) = (f x, g y, h z)
+
+mapTup3M :: Applicative m => (a -> m b) -> (a, a, a) -> m (b, b, b)
+mapTup3M f = appTup3M f f f
+
+appTup3M :: Applicative m =>
+	(a -> m b) -> (c -> m d) -> (e -> m f) -> (a, c, e) -> m (b, d, f)
+appTup3M f g h (x, y, z) = (,,) <$> f x <*> g y <*> h z
+
+mapTup3M_ :: Applicative m => (a -> m b) -> (a, a, a) -> m ()
+mapTup3M_ f = void . mapTup3M f
+
+appTup3M_ :: Applicative m =>
+	(a -> m b) -> (c -> m d) -> (e -> m f) -> (a, c, e) -> m ()
+appTup3M_ f g h = void . appTup3M f g h
diff --git a/test/Spec.hs b/test/Spec.hs
new file mode 100644
--- /dev/null
+++ b/test/Spec.hs
@@ -0,0 +1,2 @@
+main :: IO ()
+main = putStrLn "Test suite not yet implemented"
diff --git a/tools-yj.cabal b/tools-yj.cabal
new file mode 100644
--- /dev/null
+++ b/tools-yj.cabal
@@ -0,0 +1,76 @@
+cabal-version: 2.2
+
+-- This file has been generated from package.yaml by hpack version 0.37.0.
+--
+-- see: https://github.com/sol/hpack
+
+name:           tools-yj
+version:        0.1.0.19
+synopsis:       Tribial tools
+description:    Please see the README on GitHub at <https://github.com/YoshikuniJujo/tools-yj#readme>
+category:       Tools
+homepage:       https://github.com/YoshikuniJujo/tools-yj#readme
+bug-reports:    https://github.com/YoshikuniJujo/tools-yj/issues
+author:         Yoshikuni Jujo
+maintainer:     yoshikuni.jujo@gmail.com
+copyright:      Copyright (c) 2023 Yoshikuni Jujo
+license:        BSD-3-Clause
+license-file:   LICENSE
+build-type:     Simple
+extra-doc-files:
+    README.md
+    CHANGELOG.md
+
+source-repository head
+  type: git
+  location: https://github.com/YoshikuniJujo/tools-yj
+
+library
+  exposed-modules:
+      Control.Concurrent.STM.ToolsYj
+      Data.Bits.ToolsYj
+      Data.Bool.ToolsYj
+      Data.Either.ToolsYj
+      Data.Function.ToolsYj
+      Data.IORef.ToolsYj
+      Data.List.ToolsYj
+      Data.Maybe.ToolsYj
+      Data.Ord.ToolsYj
+      Data.Sequences.ToolsYj
+      Data.Text.ToolsYj
+      Data.Tuple.ToolsYj
+  other-modules:
+      Paths_tools_yj
+  autogen-modules:
+      Paths_tools_yj
+  hs-source-dirs:
+      src
+  ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-export-lists -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints
+  build-depends:
+      base >=4.7 && <5
+    , containers <1
+    , data-default <1
+    , mono-traversable <2
+    , stm <3
+    , text <3
+  default-language: Haskell2010
+
+test-suite tools-yj-test
+  type: exitcode-stdio-1.0
+  main-is: Spec.hs
+  other-modules:
+      Paths_tools_yj
+  autogen-modules:
+      Paths_tools_yj
+  hs-source-dirs:
+      test
+  ghc-options: -Wall -Wcompat -Widentities -Wincomplete-record-updates -Wincomplete-uni-patterns -Wmissing-export-lists -Wmissing-home-modules -Wpartial-fields -Wredundant-constraints -threaded -rtsopts -with-rtsopts=-N
+  build-depends:
+      base >=4.7 && <5
+    , containers <1
+    , data-default <1
+    , mono-traversable <2
+    , stm <3
+    , text <3
+    , tools-yj
+  default-language: Haskell2010