I wrote a few variants for fun. Probably equally inefficient. I suggest you look at Data.Binary as Andrew suggested. -- Your original function, but with a more generic type signature. encodeBits :: Bits n => [Bool] -> n encodeBits bs = go 0 0 bs where go n r [] = r go n r (b:bs) = go (n+1) (if b then setBit r n else clearBit r n) bs -- Combine the flags with their index and then set bits when appropriate. encodeBits2 :: Bits n => [Bool] -> n encodeBits2 = foldr (\(n, b) x -> setBitIf b x n) 0 . zip [0..] where setBitIf False x _ = x setBitIf True x n = setBit x n -- Shift the result left while constructing and only toggle the first bit. encodeBits3 :: Bits n => [Bool] -> n encodeBits3 bs = foldr (\b x -> setBitIf b (x `shiftL` 1)) 0 bs where setBitIf False x = x setBitIf True x = setBit x 0