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{-# LANGUAGE TemplateHaskell #-}
{-# OPTIONS_GHC -fno-warn-missing-signatures -fno-warn-type-defaults #-}
module Class
( DefaultsTest(..)
, defaultsTest
) where
import Language.Haskell.TH.FlexibleDefaults
import Data.Char
import Data.Monoid
import qualified Data.Map as M
import qualified Data.Set as S
-- A very silly example. For a real-world example, see the random-source package:
-- https://github.com/mokus0/random-fu/blob/master/random-source/src/Data/Random/Internal/TH.hs
class DefaultsTest a where
foo :: a -> String
foo = error "foo not implemented"
bar :: a -> Int
bar = error "bar not implemented"
baz :: a -> a -> a
baz = error "baz not implemented"
qux :: a -> Integer
qux = error "qux not implemented"
quux :: a -> Bool
quux = error "quux not implemented"
defaults :: Defaults (Sum Int) ()
defaults = scoreBy Sum $ do
function "foo" $ do
implementation $ do
cost 1
return [d| foo = filter isDigit . show |]
function "bar" $ do
implementation $ do
dependsOn "qux"
return [d| bar = fromInteger . qux |]
function "baz" $ do
implementation $ do
score 1
dependsOn "quux"
return [d| baz x | quux x = const x
| otherwise = id
|]
implementation $ do
return [d| baz = const |]
function "qux" $ do
implementation $ do
dependsOn "foo"
return [d| qux = read . foo |]
function "quux" $ do
implementation $ do
cost 1
dependsOn "foo"
return [d| quux x = toInteger (read (foo x) :: Int) == read (foo x) |]
implementation $ do
dependsOn "bar"
dependsOn "qux"
return [d| quux x = toInteger (bar x) == qux x |]
defaultsTest = withDefaults defaults
|
