I am going over the messages in this thread slowly, because this subject requires some thought. But that also means that some of my responses in this thread will appear slowly.
Anyways: On Thu, Jan 30, 2014 at 1:02 PM, Pascal Jasmin <godspiral2...@yahoo.ca> wrote: > http://repl.it/languages/Python is a useful resource for figuring out python > code. But here is the only part I had trouble understanding: > > leftmostbit =: 2&#.@:({. , 0 $~ 2 -~ #)@:(2&#. inv) NB. for some reason > divides msb by 2. Here was the version I came up with: leftmostBit=: </\&.#: If I compare this to the python code: def leftmost_bit( x ): assert x > 0 result = 1 while result <= x: result = 2 * result return result // 2 The python variable 'result' is indeed divided by 2 (// in python is like <.@% in J), but notice that there's an extra 2 * result in the loop when result is equal to x. Example use: leftmostBit"0 i.10 0 1 2 2 4 4 4 4 8 8 And here's the comparable python (leaving out 0 because of the assert): [leftmost_bit(x) for x in range(1,10)] [1, 2, 2, 4, 4, 4, 4, 8, 8] Anyways, python is a bit quirky (but maybe that is a characteristic of any computer system), but inspecting the data can work there just as it can work in J. Thanks, -- Raul ---------------------------------------------------------------------- For information about J forums see http://www.jsoftware.com/forums.htm
