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{-# LANGUAGE BangPatterns, MagicHash #-}
module Main where
import Data.Bits (finiteBitSize)
import GHC.Exts
main :: IO ()
main = do
-- 0 is the annihilator of andI#
print (I# (maxI# `andI#` 0#) == 0)
print (I# (minI# `andI#` 0#) == 0)
print (I# (0# `andI#` maxI#) == 0)
print (I# (0# `andI#` minI#) == 0)
print (I# (0# `andI#` 0#) == 0)
-- integer with all bits set to 1 is the neutral element of orI#,
-- in two's complement this is -1
print (I# (maxI# `andI#` -1#) == maxI)
print (I# (minI# `andI#` -1#) == minI)
print (I# (-1# `andI#` maxI#) == maxI)
print (I# (-1# `andI#` minI#) == minI)
print (I# (-1# `andI#` -1#) == -1)
-- these two numbers have every other bit set, they should give 0
print (I# (magicInt1# `andI#` magicInt2#) == 0)
-- integer with all bits set to 1 is the annihilator of orI#,
print (I# (maxI# `orI#` -1#) == -1)
print (I# (minI# `orI#` -1#) == -1)
print (I# (-1# `orI#` maxI#) == -1)
print (I# (-1# `orI#` minI#) == -1)
print (I# (-1# `orI#` -1#) == -1)
-- 0 is the neutral element of orI#
print (I# (maxI# `orI#` 0#) == maxI)
print (I# (minI# `orI#` 0#) == minI)
print (I# (0# `orI#` maxI#) == maxI)
print (I# (0# `orI#` minI#) == minI)
print (I# (0# `orI#` 0#) == 0)
-- this time we should get an integer with all bits set, that is -1
print (I# (magicInt1# `orI#` magicInt2#) == -1)
-- surprising as the first two tests may look, this is what we expect from
-- bitwise negation in two's complement enccoding
print (I# (notI# 0#) == -1)
print (I# (notI# -1#) == 0)
-- magic int numbers are bitwise complementary
print (I# (notI# magicInt1#) == magicInt2)
print (I# (notI# magicInt2#) == magicInt1)
-- 0 is the identity of xor
print (I# (minI# `xorI#` 0#) == minI)
print (I# (maxI# `xorI#` 0#) == maxI)
print (I# (0# `xorI#` minI#) == minI)
print (I# (0# `xorI#` maxI#) == maxI)
-- anything xored with itself is 0
print (I# (maxI# `xorI#` maxI#) == 0)
print (I# (minI# `xorI#` minI#) == 0)
-- xoring with -1 is like bitwise negation (because -1 has all bits set to 1)
print (I# (minI# `xorI#` -1#) == maxI)
print (I# (maxI# `xorI#` -1#) == minI)
print (I# (-1# `xorI#` minI#) == maxI)
print (I# (-1# `xorI#` maxI#) == minI)
-- since these two have exactly the opposite bits turned on they should
-- give an int with all bits set, and that is -1 as you probably already
-- remember by now
print (I# (magicInt1# `xorI#` magicInt2#) == -1)
where
intBitSize = finiteBitSize (undefined :: Int)
minI = minBound :: Int
maxI = maxBound :: Int
minI# = x
where !(I# x) = minBound
maxI# = x
where !(I# x) = maxBound
magicInt1 = sum $ map (2^) [0,2..intBitSize] :: Int
magicInt2 = sum $ map (2^) [1,3..intBitSize] :: Int
magicInt1# = x
where !(I# x) = magicInt1
magicInt2# = x
where !(I# x) = magicInt2
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