base-compat-0.7.1: A compatibility layer for base

Safe HaskellSafe-Inferred
LanguageHaskell98

Data.Bits.Compat

Synopsis

Documentation

class Eq a => Bits a where

The Bits class defines bitwise operations over integral types.

  • Bits are numbered from 0 with bit 0 being the least significant bit.

Minimal complete definition: .&., .|., xor, complement, (shift or (shiftL and shiftR)), (rotate or (rotateL and rotateR)), bitSize, isSigned, testBit, bit, and popCount. The latter three can be implemented using testBitDefault, bitDefault, and popCountDefault, if a is also an instance of Num.

Minimal complete definition

(.&.), (.|.), xor, complement, (shift | shiftL, shiftR), (rotate | rotateL, rotateR), bitSize, bitSizeMaybe, isSigned, testBit, bit, popCount

Methods

(.&.) :: a -> a -> a infixl 7

Bitwise "and"

(.|.) :: a -> a -> a infixl 5

Bitwise "or"

xor :: a -> a -> a infixl 6

Bitwise "xor"

complement :: a -> a

Reverse all the bits in the argument

shift :: a -> Int -> a infixl 8

shift x i shifts x left by i bits if i is positive, or right by -i bits otherwise. Right shifts perform sign extension on signed number types; i.e. they fill the top bits with 1 if the x is negative and with 0 otherwise.

An instance can define either this unified shift or shiftL and shiftR, depending on which is more convenient for the type in question.

rotate :: a -> Int -> a infixl 8

rotate x i rotates x left by i bits if i is positive, or right by -i bits otherwise.

For unbounded types like Integer, rotate is equivalent to shift.

An instance can define either this unified rotate or rotateL and rotateR, depending on which is more convenient for the type in question.

zeroBits :: a

zeroBits is the value with all bits unset.

The following laws ought to hold (for all valid bit indices n):

This method uses clearBit (bit 0) 0 as its default implementation (which ought to be equivalent to zeroBits for types which possess a 0th bit).

Since: 4.7.0.0

bit :: Int -> a

bit i is a value with the ith bit set and all other bits clear.

See also zeroBits.

setBit :: a -> Int -> a

x `setBit` i is the same as x .|. bit i

clearBit :: a -> Int -> a

x `clearBit` i is the same as x .&. complement (bit i)

complementBit :: a -> Int -> a

x `complementBit` i is the same as x `xor` bit i

testBit :: a -> Int -> Bool

Return True if the nth bit of the argument is 1

bitSizeMaybe :: a -> Maybe Int

Return the number of bits in the type of the argument. The actual value of the argument is ignored. Returns Nothing for types that do not have a fixed bitsize, like Integer.

Since: 4.7.0.0

bitSize :: a -> Int

Return the number of bits in the type of the argument. The actual value of the argument is ignored. The function bitSize is undefined for types that do not have a fixed bitsize, like Integer.

isSigned :: a -> Bool

Return True if the argument is a signed type. The actual value of the argument is ignored

shiftL :: a -> Int -> a infixl 8

Shift the argument left by the specified number of bits (which must be non-negative).

An instance can define either this and shiftR or the unified shift, depending on which is more convenient for the type in question.

unsafeShiftL :: a -> Int -> a

Shift the argument left by the specified number of bits. The result is undefined for negative shift amounts and shift amounts greater or equal to the bitSize.

Defaults to shiftL unless defined explicitly by an instance.

Since: 4.5.0.0

shiftR :: a -> Int -> a infixl 8

Shift the first argument right by the specified number of bits. The result is undefined for negative shift amounts and shift amounts greater or equal to the bitSize.

Right shifts perform sign extension on signed number types; i.e. they fill the top bits with 1 if the x is negative and with 0 otherwise.

An instance can define either this and shiftL or the unified shift, depending on which is more convenient for the type in question.

unsafeShiftR :: a -> Int -> a

Shift the first argument right by the specified number of bits, which must be non-negative an smaller than the number of bits in the type.

Right shifts perform sign extension on signed number types; i.e. they fill the top bits with 1 if the x is negative and with 0 otherwise.

Defaults to shiftR unless defined explicitly by an instance.

Since: 4.5.0.0

rotateL :: a -> Int -> a infixl 8

Rotate the argument left by the specified number of bits (which must be non-negative).

An instance can define either this and rotateR or the unified rotate, depending on which is more convenient for the type in question.

rotateR :: a -> Int -> a infixl 8

Rotate the argument right by the specified number of bits (which must be non-negative).

An instance can define either this and rotateL or the unified rotate, depending on which is more convenient for the type in question.

popCount :: a -> Int

Return the number of set bits in the argument. This number is known as the population count or the Hamming weight.

Since: 4.5.0.0

Instances