Thread: bitwise ops

Apparently native Lua has no bitwise operators. Also, apparently EffectCategories are bit fields. Any chance bitwise operator support could be added?

I ended up adding my own bitop support. I got the code somewhere off the net, don't remember where and then modified it for my plugins use:

Code:

-- get the actual value of the 1 based index of the bit
DhorPlugins.bit = function(p)
  return 2 ^ (p - 1);
end

-- Typical call:  if hasbit(x, bit(3)) then ...
DhorPlugins.hasbit = function(x, p)
  if(x % (p + p) >= p) then
	return true;
  else
	return false;
  end    
end

DhorPlugins.setbit = function(x, p)
  return hasbit(x, p) and x or x + p;
end

DhorPlugins.clearbit = function(x, p)
  return hasbit(x, p) and x - p or x;
end

DhorPlugins.togglebit = function(x, p)
	if(hasbit(x,p)) then
		return clearbit(x,p);
	else
		return setbit(x,p);
	end	
end

Just change the DhorPlugins part to whatever you need.....

But I do agree, it would be nice if it was built into LUA. I think this would be more of a LUA request, than a Turbine API request.

I recently had need of bitwise AND and bitwise OR functions so I wrote these two:

Code:

function band(x,y)
  local x2=math.floor(x/2)
  local y2=math.floor(y/2)
  local z=0;
  if x2~=0 and y2~=0 then
    z=band(x2,y2)*2
  end
  if math.fmod(x,2)==1 and math.fmod(y,2)==1 then
    z=z+1
  end
  return z
end
function bor(x,y)
  local x2=math.floor(x/2)
  local y2=math.floor(y/2)
  local z=0;
  if x~=0 or y2~=0 then
    z=bor(x2,y2)*2
  end
  if math.fmod(x,2)==1 or math.fmod(y,2)==1 then
    z=z+1
  end
  return z
end

They aren't nearly as efficient as a C version would be so it would still be nice if Turbine could add a bit class which supported the functions Dhor previously published as well as bitwise AND, OR and NOT functions.