cli/Hcompta/Expr/If.hs

   1 {-# LANGUAGE DefaultSignatures #-}
   2 {-# LANGUAGE NoImplicitPrelude #-}
   3 {-# OPTIONS_GHC -fno-warn-tabs #-}
   4
   5 module Hcompta.Expr.If where
   6
   7 import Control.Monad (Monad(..), when)
   8 import Data.Bool
   9
  10 import Hcompta.Expr.Dup
  11
  12 -- * Class 'Expr_If'
  13
  14 class Expr_If repr where
  15         default if_   :: Monad repr => repr Bool -> repr a -> repr a -> repr a
  16         default when_ :: Monad repr => repr Bool -> repr () -> repr ()
  17
  18         if_ :: repr Bool -> repr a -> repr a -> repr a
  19         if_ m ok ko = do
  20                 m' <- m
  21                 if m' then ok else ko
  22
  23         when_ :: repr Bool -> repr () -> repr ()
  24         when_ m ok = do
  25                 m' <- m
  26                 when m' ok
  27
  28 instance -- Expr_If Dup
  29  ( Expr_If r1
  30  , Expr_If r2
  31  ) => Expr_If (Dup r1 r2) where
  32         if_ (c1 `Dup` c2) (ok1 `Dup` ok2) (ko1 `Dup` ko2) =
  33                 if_ c1 ok1 ko1 `Dup`
  34                 if_ c2 ok2 ko2
  35         when_ (c1 `Dup` c2) (ok1 `Dup` ok2) =
  36                 when_ c1 ok1 `Dup`
  37                 when_ c2 ok2