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Diffstat (limited to 'third_party/bazel/rules_haskell/examples/vector/Data/Vector/Generic/Base.hs')
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1 files changed, 140 insertions, 0 deletions
diff --git a/third_party/bazel/rules_haskell/examples/vector/Data/Vector/Generic/Base.hs b/third_party/bazel/rules_haskell/examples/vector/Data/Vector/Generic/Base.hs new file mode 100644 index 0000000000..a760329c59 --- /dev/null +++ b/third_party/bazel/rules_haskell/examples/vector/Data/Vector/Generic/Base.hs @@ -0,0 +1,140 @@ +{-# LANGUAGE Rank2Types, MultiParamTypeClasses, FlexibleContexts, + TypeFamilies, ScopedTypeVariables, BangPatterns #-} +{-# OPTIONS_HADDOCK hide #-} + +-- | +-- Module : Data.Vector.Generic.Base +-- Copyright : (c) Roman Leshchinskiy 2008-2010 +-- License : BSD-style +-- +-- Maintainer : Roman Leshchinskiy <rl@cse.unsw.edu.au> +-- Stability : experimental +-- Portability : non-portable +-- +-- Class of pure vectors +-- + +module Data.Vector.Generic.Base ( + Vector(..), Mutable +) where + +import Data.Vector.Generic.Mutable.Base ( MVector ) +import qualified Data.Vector.Generic.Mutable.Base as M + +import Control.Monad.Primitive + +-- | @Mutable v s a@ is the mutable version of the pure vector type @v a@ with +-- the state token @s@ +-- +type family Mutable (v :: * -> *) :: * -> * -> * + +-- | Class of immutable vectors. Every immutable vector is associated with its +-- mutable version through the 'Mutable' type family. Methods of this class +-- should not be used directly. Instead, "Data.Vector.Generic" and other +-- Data.Vector modules provide safe and fusible wrappers. +-- +-- Minimum complete implementation: +-- +-- * 'basicUnsafeFreeze' +-- +-- * 'basicUnsafeThaw' +-- +-- * 'basicLength' +-- +-- * 'basicUnsafeSlice' +-- +-- * 'basicUnsafeIndexM' +-- +class MVector (Mutable v) a => Vector v a where + -- | /Assumed complexity: O(1)/ + -- + -- Unsafely convert a mutable vector to its immutable version + -- without copying. The mutable vector may not be used after + -- this operation. + basicUnsafeFreeze :: PrimMonad m => Mutable v (PrimState m) a -> m (v a) + + -- | /Assumed complexity: O(1)/ + -- + -- Unsafely convert an immutable vector to its mutable version without + -- copying. The immutable vector may not be used after this operation. + basicUnsafeThaw :: PrimMonad m => v a -> m (Mutable v (PrimState m) a) + + -- | /Assumed complexity: O(1)/ + -- + -- Yield the length of the vector. + basicLength :: v a -> Int + + -- | /Assumed complexity: O(1)/ + -- + -- Yield a slice of the vector without copying it. No range checks are + -- performed. + basicUnsafeSlice :: Int -- ^ starting index + -> Int -- ^ length + -> v a -> v a + + -- | /Assumed complexity: O(1)/ + -- + -- Yield the element at the given position in a monad. No range checks are + -- performed. + -- + -- The monad allows us to be strict in the vector if we want. Suppose we had + -- + -- > unsafeIndex :: v a -> Int -> a + -- + -- instead. Now, if we wanted to copy a vector, we'd do something like + -- + -- > copy mv v ... = ... unsafeWrite mv i (unsafeIndex v i) ... + -- + -- For lazy vectors, the indexing would not be evaluated which means that we + -- would retain a reference to the original vector in each element we write. + -- This is not what we want! + -- + -- With 'basicUnsafeIndexM', we can do + -- + -- > copy mv v ... = ... case basicUnsafeIndexM v i of + -- > Box x -> unsafeWrite mv i x ... + -- + -- which does not have this problem because indexing (but not the returned + -- element!) is evaluated immediately. + -- + basicUnsafeIndexM :: Monad m => v a -> Int -> m a + + -- | /Assumed complexity: O(n)/ + -- + -- Copy an immutable vector into a mutable one. The two vectors must have + -- the same length but this is not checked. + -- + -- Instances of 'Vector' should redefine this method if they wish to support + -- an efficient block copy operation. + -- + -- Default definition: copying basic on 'basicUnsafeIndexM' and + -- 'basicUnsafeWrite'. + basicUnsafeCopy :: PrimMonad m => Mutable v (PrimState m) a -> v a -> m () + + {-# INLINE basicUnsafeCopy #-} + basicUnsafeCopy !dst !src = do_copy 0 + where + !n = basicLength src + + do_copy i | i < n = do + x <- basicUnsafeIndexM src i + M.basicUnsafeWrite dst i x + do_copy (i+1) + | otherwise = return () + + -- | Evaluate @a@ as far as storing it in a vector would and yield @b@. + -- The @v a@ argument only fixes the type and is not touched. The method is + -- only used for optimisation purposes. Thus, it is safe for instances of + -- 'Vector' to evaluate @a@ less than it would be when stored in a vector + -- although this might result in suboptimal code. + -- + -- > elemseq v x y = (singleton x `asTypeOf` v) `seq` y + -- + -- Default defintion: @a@ is not evaluated at all + -- + elemseq :: v a -> a -> b -> b + + {-# INLINE elemseq #-} + elemseq _ = \_ x -> x + + |