Bitwise018

module Bitwise018 exposing (shiftLeftBy, shiftRightBy, shiftRightZfBy)

{-| Several functions were replaced with "flipped" versions in Elm 0.18 --
here are the new versions.

@docs shiftLeftBy, shiftRightBy, shiftRightZfBy

-}

import Bitwise


{-| Shift bits to the left by a given offset, filling new bits with zeros.
This can be used to multiply numbers by powers of two.

    shiftLeftBy 1 5 == 10
    shiftLeftBy 5 1 == 32

-}
shiftLeftBy : Int -> Int -> Int
shiftLeftBy =
    flip Bitwise.shiftLeft


{-| Shift bits to the right by a given offset, filling new bits with
whatever is the topmost bit. This can be used to divide numbers by powers of two.

    shiftRightBy 1 32 == 16
    shiftRightBy 2 32 == 8
    shiftRightBy 1 -32 == -16

This is called an [arithmetic right shift][ars], often written (>>), and
sometimes called a sign-propagating right shift because it fills empty spots
with copies of the highest bit.

[ars]: <http://en.wikipedia.org/wiki/Bitwise_operation#Arithmetic_shift>

-}
shiftRightBy : Int -> Int -> Int
shiftRightBy =
    flip Bitwise.shiftRight


{-| Shift bits to the right by a given offset, filling new bits with zeros.

    shiftRightZfBy 1 32 == 16
    shiftRightZfBy 2 32 == 8
    shiftRightZfBy 1 -32 == 2147483632

This is called an [logical right shift][lrs], often written (>>>), and
sometimes called a zero-fill right shift because it fills empty spots with
zeros.

[lrs]: <http://en.wikipedia.org/wiki/Bitwise_operation#Logical_shift>

-}
shiftRightZfBy : Int -> Int -> Int
shiftRightZfBy =
    flip Bitwise.shiftRightLogical