Merge pull request #10 from davisdude/master

Added point.lua

modules/point.lua

@@ -0,0 +1,139 @@
+--- Point module
+-- @module point
+
+local current_folder = (...):gsub('%.[^%.]+$', '') .. "."
+local point = {}
+local function new(x, y)
+	return setmetatable({
+		x, y
+	}, point)
+end
+point.__index = point
+point.__call = function(_, ...) return new(...) end
+
+--- Rotate a point, optionally about another point.
+-- @param point Table with two points as {x, y}
+-- @param rotation Radian amount to rotate
+-- @param[opt=0] offset_x Point to rotate about
+-- @param[optchain=0] offset_y offset_y Point to rotatea about
+-- @return New point rotated counter-clockwise
+function point.rotate(point, rotation, offset_x, offset_y)
+	offset_x, offset_y = offset_x or 0, offset_y or 0
+	local x, y = unpack(point)
+	local distance_x, distance_y = x - offset_x, y - offset_y
+	local cos, sin = math.cos(rotation), math.sin(rotation)
+	return new(distance_x * cos + offset_x - distance_y * sin, distance_x * sin + distance_y * cos + offset_y)
+end
+
+--- Scale a point a point, optionally about another point.
+-- @param point Table with two points as {x, y}
+-- @param scale Number or Table in the form of scale or {scaleX [, scaleY=scaleX]}
+-- @param[opt=0] offset_x Point to scale about
+-- @param[optchain=0] offset_y Point to scale about
+-- @return New scaled point
+function point.scale(point, scale, offset_x, offset_y)
+	local scale_x, scale_y
+	if type( scale ) == 'table' then
+		scale_x, scale_y = unpack(scale)
+		scale_y = scale_y or scale_x
+	elseif type( scale ) == 'number' then
+		scale_x, scale_y = scale, scale
+	end
+	offset_x, offset_y = offset_x or 0, offset_y or 0
+	local x, y = unpack(point)
+	return new((x - offset_x) * scale_x + offset_x, (y - offset_y) * scale_y + offset_y)
+end
+
+--- Translate a point.
+-- @param point Table with two points as {x, y}
+-- @param distance_x Distance to translate along the x-axis
+-- @param distance_y Distance to translate along the y-axis
+-- @return Translated point
+function point.translate(point, distance_x, distance_y)
+	return new(point[1] + distance_x, point[2] + distance_y)
+end
+
+--- Print point.
+-- @param point Table with two numbers as {x, y}
+-- @return "[ x, y ]"
+function point.__tostring(point)
+	return string.format( "[ %d, %d ]", point[1], point[2] )
+end
+
+local function ispoint( p )
+	return p[1] and p[2]
+end
+
+--- Add points.
+-- @param a Table with two numbers as {x, y} or a number
+-- @param b Table with two numbers as {x, y} or a number
+-- @return Translated point
+function point.__add(a, b)
+	if type(a) == "number" then
+		return point.translate(b, a, a)
+	elseif type(b) == "number" then
+		return point.translate(a, b, b)
+	else
+		assert(ispoint(a) and ispoint(b), "Add: wrong argument types (<point> expected)")
+		return point.translate(a, b[1], b[2])
+	end
+end
+
+--- Subtract points.
+-- @param a Table with two numbers as {x, y} or a number
+-- @param b Table with two numbers as {x, y} or a number
+-- @return Translated point
+function point.__sub(a, b)
+	if type(a) == "number" then
+		return point.translate(b, -a, -a)
+	elseif type(b) == "number" then
+		return point.translate(a, -b, -b)
+	else
+		assert(ispoint(a) and ispoint(b), "Subtract: wrong argument types (<point> expected)")
+		return point.translate(a, -b[1], -b[2])
+	end
+end
+
+--- Multiply points.
+-- @param a Table with two numbers as {x, y} or amount to scale
+-- @param b Table with two numbers as {x, y} or amount to scale
+-- @return Scaled point
+function point.__mul(a, b)
+	if type(a) == "number" then
+		return point.scale(b, a)
+	elseif type(b) == "number" then
+		return point.scale(a, b)
+	end
+	error( "Multiply: cannot multiply two points" )
+end
+
+--- Convert point from polar to cartesian.
+-- @param radius Radius of the point
+-- @param theta Angle of the point
+-- @param[opt=0] offset_radius Distance from origin
+-- @param[optchain=0] offset_theta Angle for offset
+-- @return Converted point
+function point.from_polar(radius, theta, offset_radius, offset_theta)
+	local offset_x, offset_y = 0, 0
+	if offset_radius and offset_theta then
+		offset_x, offset_y = point.from_polar(offset_radius, offset_theta)
+	end
+	return new(radius * math.cos(theta) + offset_x, radius * math.sin(theta) + offset_y)
+end
+
+--- Convert point from cartesian to polar.
+-- @param point Table with two numbers as {x, y}
+-- @param[opt=0] offset_x Horizontal offset
+-- @param[optchain=0] offset_y Vertical offset
+-- @return Table in the form {radius, theta}
+function point.to_polar(point, offset_x, offset_y)
+	local offset_x, offset_y = offset_x or 0, offset_y or 0
+	local x, y = point[1] - offset_x, point[2] - offset_y
+	local theta = math.atan2(y, x)
+	-- Convert to absolute angle
+	theta = theta > 0 and theta or theta + 2 * math.pi
+	local radius = math.sqrt(x ^ 2 + y ^ 2)
+	return {radius, theta}
+end
+
+return setmetatable({new = new}, point)