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Memory allocation: Difference between revisions
Added Haskell implementation
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make(map[int]int)
make(chan int)</lang>
=={{header|Haskell}}==
You usually only need to do low-level memory management in Haskell when interfacing with code written in other languages (particularly C). At its most basic level, Haskell provides malloc()/free()-like operations in the IO monad.
<lang Haskell>import Foreign
bytealloc :: IO ()
bytealloc = do
a0 <- mallocBytes 100 -- Allocate 100 bytes
free a0 -- Free them again
allocaBytes 100 $ \a -> -- Allocate 100 bytes; automatically
-- freed when closure finishes
poke (a::Ptr Word32) 0</lang>
Slightly more sophisticated functions are available for automatically determining the amount of memory necessary to store a value of a specific type. The type is determined by type inference (in this example I use explicit manual type annotations, because poke is polymorphic).
<lang Haskell>import Foreign
typedalloc :: IO ()
typedalloc = do
w <- malloc
poke w (100 :: Word32)
free w
alloca $ \a -> poke a (100 :: Word32)</lang>
By the typing rules of Haskell, w must have the type 'Ptr Word32' (pointer to 32-bit word), which is how malloc knows how much memory to allocate.
=={{header|J}}==
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