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--------------------------------------------------------------------------
-- point.lua
--------------------------------------------------------------------------
local point_metatable = { }
point_metatable.__index = point_metatable
function dgn.point(x, y)
local pt = { x = x, y = y }
setmetatable(pt, point_metatable)
return pt
end
local function sgn(x)
if x < 0 then
return -1
elseif x > 0 then
return 1
else
return 0
end
end
point_metatable.sgn = function (p)
return dgn.point(sgn(p.x), sgn(p.y))
end
point_metatable.__eq = function (a, b)
return a.x == b.x and a.y == b.y
end
point_metatable.__add = function (a, b)
if type(b) == "number" then
return dgn.point(a.x + b, a.y + b)
else
return dgn.point(a.x + b.x, a.y + b.y)
end
end
point_metatable.__sub = function (a, b)
if type(b) == "number" then
return dgn.point(a.x - b, a.y - b)
else
return dgn.point(a.x - b.x, a.y - b.y)
end
end
point_metatable.__div = function (a, b)
if type(b) ~= "number" then
error("Can only divide by numbers.")
end
return dgn.point(math.floor(a.x / b),
math.floor(a.y / b))
end
point_metatable.__mul = function (a, b)
if type(b) ~= "number" then
error("Can only multiply by numbers.")
end
return dgn.point(a.x * b, a.y * b)
end
point_metatable.__unm = function (a)
return dgn.point(-a.x, -a.y)
end
point_metatable.__concat = function (pre, post)
local function pstr(p)
return "(" .. p.x .. "," .. p.y .. ")"
end
if getmetatable(pre) == point_metatable then
return pstr(pre) .. post
else
return pre .. pstr(post)
end
end
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