group-with (empty) → 0.1.0.0
raw patch · 6 files changed
+391/−0 lines, 6 filesdep +Cabaldep +QuickCheckdep +basesetup-changed
Dependencies added: Cabal, QuickCheck, base, containers, hspec, hspec-expectations
Files
- Control/GroupWith.hs +67/−0
- GroupWithTest.hs +78/−0
- LICENSE +202/−0
- README.md +4/−0
- Setup.hs +2/−0
- group-with.cabal +38/−0
+ Control/GroupWith.hs view
@@ -0,0 +1,67 @@++-----------------------------------------------------------------------------+-- |+-- Module : Control.GroupWiths+-- Copyright : (c) Uli Köhler 2014+-- License : Apache License v2.0+-- Maintainer : ukoehler@techoverflow.net+-- Stability : provisional+-- Portability : portable+--+-- A collection of grouping utility functions.+-- For a given function that assigns a key to objects,+-- provides functions that group said objects into a multimap+-- by said key.+--+-- This can be used similarly to the SQL GROUP BY statement.+--+-- Provides a more flexible approach to GHC.Exts.groupWith+--+-- > groupWith (take 1) ["a","ab","bc"] == Map.fromList [("a",["a","ab"]), ("b",["bc"])]+-- +-----------------------------------------------------------------------------+module Control.GroupWith(+ MultiMap,+ groupWith,+ groupWithMultiple,+ groupWithUsing+ ) where++import Data.Map (Map)+import qualified Data.Map as Map++type MultiMap a b = Map a [b]++-- | Group values in a list by a key, generated+-- by a given function. The resulting map contains+-- for each generated key the values (from the given list)+-- that yielded said key by applying the function on said value.+groupWith :: (Ord b) =>+ (a -> b) -- ^ The function used to map a list value to its key+ -> [a] -- ^ The list to be grouped+ -> MultiMap b a -- ^ The resulting key --> value multimap+groupWith f xs = Map.fromListWith (++) [(f x, [x]) | x <- xs]++-- | Like groupWith, but the identifier-generating function+-- may generate multiple keys for each value (or none at all).+-- The corresponding value from the original list will be placed+-- in the identifier-corresponding map entry for each generated+-- identifier.+-- Note that values are added to the +groupWithMultiple :: (Ord b) =>+ (a -> [b]) -- ^ The function used to map a list value to its keys+ -> [a] -- ^ The list to be grouped+ -> MultiMap b a -- ^ The resulting map+groupWithMultiple f xs = + let identifiers x = [(val, [x]) | val <- f x]+ in Map.fromListWith (++) $ concat [identifiers x | x <- xs]++-- | Like groupWith, but uses a custom combinator function+groupWithUsing :: (Ord b) =>+ (a -> c) -- ^ Transformer function used to map a value to the resulting type+ -> (c -> c -> c) -- ^ The combinator used to combine an existing value+ -- for a given key with a new value+ -> (a -> b) -- ^ The function used to map a list value to its key+ -> [a] -- ^ The list to be grouped+ -> Map b c -- ^ The resulting key --> transformed value map+groupWithUsing t c f xs = Map.fromListWith c $ map (\v -> (f v, t v)) xs
+ GroupWithTest.hs view
@@ -0,0 +1,78 @@+import Test.Hspec+import Test.QuickCheck+import Control.Exception (evaluate)+import Control.Monad+import Control.GroupWith+import Data.Map (Map)+import Data.List (sort)+import qualified Data.Map as Map++multimapElemEq :: (Eq k, Ord v) => (k,[v]) -> (k,[v]) -> Bool+multimapElemEq (k1,v1) (k2,v2) = (k1 == k2) && (sort v1 == sort v2)++-- Check if two multimap-representing lists are equal,+-- disregarding value list order+multimapListEq :: (Ord a, Ord b, Eq a, Eq b) => [(a,[b])] -> [(a,[b])] -> Bool+multimapListEq xs ys =+ let zipped = zipWith multimapElemEq xs ys+ in and zipped++multimapEq :: (Ord a, Ord b, Eq a, Eq b) => Map a [b] -> Map a [b] -> Bool+multimapEq x y =+ multimapListEq (Map.toList x) (Map.toList y)++multimapTupleEq :: (Ord a, Ord b, Eq a, Eq b) => (Map a [b], Map a [b]) -> Bool+multimapTupleEq (x,y) = multimapEq x y++main :: IO ()+main = hspec $ do+ describe "groupWith" $ do+ it "should group a simple value correctly" $+ let data_ = ["a","abc","ab","bc"]+ fn = take 1+ ref = Map.fromList [("a",["a","abc","ab"]),("b",["bc"])]+ result = groupWith fn data_+ in (result, ref) `shouldSatisfy` multimapTupleEq+ it "should return an empty map when given an empty list" $+ -- We need to specialize here, because it's ⊥+ let fn = error "This function should never be called" :: Int -> Int+ data_ = [] :: [Int]+ result = groupWith fn data_+ in result `shouldSatisfy` ((==) 0 . Map.size)+ -- Fuzzing, couldn't get this to compile properly yet+ -- it "should not crash for any input string list" $+ -- property $ (\d -> groupWith (take 1) d `seq` True)+ describe "groupWithUsing" $ do+ it "should return an empty map when given an empty list" $+ -- We need to specialize here, because it's ⊥+ let fn = error "This function should never be called" :: Int -> Int+ data_ = [] :: [Int]+ result = groupWith fn data_+ in result `shouldSatisfy` ((==) 0 . Map.size)+ it "should be usable for counting" $+ -- Instead of building up lists, we count the number of elements+ let t n = 1 -- For each x, count 1+ c = (+) -- Sum up the counts+ fn = take 1+ data_ = ["a","abc","ab","bc"]+ ref = Map.fromList [("a",3),("b",1)] :: Map String Int+ result = groupWithUsing t c fn data_+ in result `shouldBe` ref+ describe "groupWithMultiple" $ do+ it "should group correctly given a simple list" $+ let data_ = ["a","abc","ab","bc"]+ fn x = [take 1 x, take 2 x]+ -- Note the multiple "a"s in the first line:+ -- one from `take 1`, one from `take 2`+ ref = Map.fromList [("a",["a","a","abc","ab"]),+ ("ab",["ab","abc"]),+ ("b",["bc"]),+ ("bc",["bc"])]+ result = groupWithMultiple fn data_+ in (result, ref) `shouldSatisfy` multimapTupleEq+ it "should return an empty map when given an empty list" $+ -- We need to specialize here, because it's ⊥+ let fn = error "This function should never be called" :: Int -> [Int]+ data_ = [] :: [Int]+ result = groupWithMultiple fn data_+ in result `shouldSatisfy` ((==) 0 . Map.size)
+ LICENSE view
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+ README.md view
@@ -0,0 +1,4 @@+group-by+========++A Haskell library to classify objects by a function value, just like SQL GROUP BY
+ Setup.hs view
@@ -0,0 +1,2 @@+import Distribution.Simple+main = defaultMain
+ group-with.cabal view
@@ -0,0 +1,38 @@+name: group-with+version: 0.1.0.0+synopsis: Classify objects by key-generating function, like SQL GROUP BY+description: A library to classify objects into multimaps by using a function generating+ keys for any object in the list.++ This allows an approach similar to SQL GROUP BY.++ Provides a more flexible approach to `GHC.Exts.groupWith`.+homepage: https://github.com/ulikoehler/group-with+license: Apache-2.0+license-file: LICENSE+author: Uli Köhler+maintainer: ukoehler@techoverflow.net+-- copyright: +category: Data+build-type: Simple+extra-source-files: README.md+cabal-version: >=1.10++source-repository head+ type: git+ location: https://github.com/ulikoehler/group-with++library+ exposed-modules: Control.GroupWith+ -- other-modules:+ -- other-extensions:+ build-depends: base >= 4.2 && < 4.8, containers >= 0.3+ -- hs-source-dirs:+ default-language: Haskell2010++Test-Suite test-groupby+ type: exitcode-stdio-1.0+ main-is: GroupWithTest.hs+ default-language: Haskell2010+ build-depends: base, Cabal >= 1.9.2, hspec, hspec-expectations,+ containers >= 0.3, QuickCheck