base-compat-0.12.1: A compatibility layer for base

Safe Haskell | Safe-Inferred
Language | Haskell2010

Data.Bits.Compat

Synopsis

- module Data.Bits
- bitDefault :: (Bits a, Num a) => Int -> a
- testBitDefault :: (Bits a, Num a) => a -> Int -> Bool
- popCountDefault :: (Bits a, Num a) => a -> Int
- toIntegralSized :: (Integral a, Integral b, Bits a, Bits b) => a -> Maybe b

# Documentation

module Data.Bits

bitDefault :: (Bits a, Num a) => Int -> a #

Default implementation for `bit`.

Note that: `bitDefault i = 1 `shiftL` i`

Since: base-4.6.0.0

testBitDefault :: (Bits a, Num a) => a -> Int -> Bool #

Default implementation for `testBit`.

Note that: `testBitDefault x i = (x .&. bit i) /= 0`

Since: base-4.6.0.0

popCountDefault :: (Bits a, Num a) => a -> Int #

Default implementation for `popCount`.

This implementation is intentionally naive. Instances are expected to provide an optimized implementation for their size.

Since: base-4.6.0.0

toIntegralSized :: (Integral a, Integral b, Bits a, Bits b) => a -> Maybe b #

Attempt to convert an `Integral` type `a` to an `Integral` type `b` using the size of the types as measured by `Bits` methods.

A simpler version of this function is:

    toIntegral :: (Integral a, Integral b) => a -> Maybe b
    toIntegral x
      | toInteger x == y = Just (fromInteger y)
      | otherwise        = Nothing
      where
        y = toInteger x

This version requires going through `Integer`, which can be inefficient. However, `toIntegralSized` is optimized to allow GHC to statically determine the relative type sizes (as measured by `bitSizeMaybe` and `isSigned`) and avoid going through `Integer` for many types. (The implementation uses `fromIntegral`, which is itself optimized with rules for `base` types but may go through `Integer` for some type pairs.)

Since: base-4.8.0.0