Created
November 2, 2010 17:31
-
-
Save sebastian/659971 to your computer and use it in GitHub Desktop.
Does binary addition of two bitstrings of equal length and throws away the carry.
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
-spec(add_bitstrings/2::(Bin1::bitstring(), Bin2::bitstring()) -> bitstring()). | |
add_bitstrings(Bin1, Bin2) when bit_size(Bin1) =:= bit_size(Bin2) -> | |
add_bit_with_carry(bit_size(Bin1), Bin1, Bin2, false). | |
add_bit_with_carry(0, Acc, _Bin, _Carry) -> Acc; | |
add_bit_with_carry(BitNumber, AccBin1, Bin2, Carry) -> | |
Bit = BitNumber - 1, | |
<<Beginning:Bit/bitstring, B1:1/bitstring, Rest/bitstring>> = AccBin1, | |
<<_DontYetCare:Bit/bitstring, B2:1/bitstring, _Rest/bitstring>> = Bin2, | |
{NextBit, NextCarry} = case {B1, B2, Carry} of | |
{<<0:1>>, <<0:1>>, true} -> {1, false}; | |
{<<0:1>>, <<0:1>>, false} -> {0, false}; | |
{<<0:1>>, <<1:1>>, true} -> {0, true}; | |
{<<0:1>>, <<1:1>>, false} -> {1, false}; | |
{<<1:1>>, <<0:1>>, true} -> {0, true}; | |
{<<1:1>>, <<0:1>>, false} -> {1, false}; | |
{<<1:1>>, <<1:1>>, true} -> {1, true}; | |
{<<1:1>>, <<1:1>>, false} -> {0, true} | |
end, | |
<<_:7/bitstring, B:1/bitstring>> = <<NextBit>>, | |
add_bit_with_carry(Bit, | |
<<Beginning:Bit/bitstring, B:1/bitstring, Rest/bitstring>>, | |
Bin2, NextCarry). |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment