Re: [Haskell-cafe] Please explain behavior of setBit

On 11/13/05, Murray Gross wrote:

Here is my trivial program:

import Bits

main = putStr (show(bit 0::Int)++" "++show (mybit 0))

mybit:: Int -> Int mybit x = setBit (bit 0) x

The output (with GHC-5) is

1 1

My question: Why is (bit 0) equal to 1 and not 0?

If only the first bit in an Integer is set then the number is equal to 1.

That first bit is set regardless of the value of x (I have tried several), although in each case, the bit I expect to be set is also set (e.g., mybit 4 yields 17).

http://haskell.org/ghc/docs/latest/html/libraries/base/Data-Bits.html 'setBit (bit 0) 4' => 'setBit 1 4' => (binary) 10001 => (dec) 17 You're setting the fifth bit in '1' instead of setting the seconded bit in '4'. -- Friendly, Lemmih