gen=require("gen")
printf=gen.printf
floor=math.floor
sqrt=math.sqrt
abs=math.abs

local function dbg(...)
	if DBG then
		print(...)
	end
end

-- original tpr() is in "gen.lua"
-- improved 
local function tpr(...)
	t = {...}
	if type(t[1])=="string" then
		print(t[1])
		remove(t,1)
	end
	local i
	a = t[1]
	for i=#a,0,-1 do
		print(i,a[i])
	end
	for k,v in pairs(a) do
		if type(k)~="number" then print(k,v) end
	end
end

local function dup(t)
	-- create new table from t
	local tn
	tn = {}
	for k,v in pairs(t) do
		if type(v)=="table" then
			tn[k] = dup(v)
		else
			tn[k] = v
		end
	end
	return tn
end

local function gcd(a,b)
	-- a,b: int
	--print("gcd")
	local c
	a = abs(a)
	b = abs(b)
	assert(a+b>0)
	while b > 0 do
		c = a % b
		a,b = b,c
		--print("a,b,c",a,b,c)
	end
	return a
end
--[[
print("gcd")
print(gcd(12,15))	--> 3
print(gcd(0,15))	--> 15
print(gcd(0,0))	-->fail
os.exit()
--]]

return {
  dbg=dbg,
  tpr=tpr,
  dup=dup,
  gcd=gcd,
}