125 lines
2.6 KiB
Go
125 lines
2.6 KiB
Go
// Package geo implements basic geometric concepts used by gim
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package geo
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import "math"
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// XY describes a 2-dimensional position or vector. The origin of the
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// 2-dimensional space is a 0,0, with the x-axis going to the left and the
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// y-axis going down.
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type XY [2]int
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// Zero is the zero point, or a zero vector, depending on what you're doing
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var Zero = XY{0, 0}
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// Unit vectors
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var (
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Up = XY{0, -1}
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Down = XY{0, 1}
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Left = XY{-1, 0}
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Right = XY{1, 0}
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)
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// Units is the set of unit vectors
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var Units = []XY{
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Up,
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Down,
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Left,
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Right,
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}
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func (xy XY) toF64() [2]float64 {
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return [2]float64{
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float64(xy[0]),
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float64(xy[1]),
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}
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}
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func abs(i int) int {
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if i < 0 {
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return i * -1
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}
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return i
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}
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// Len returns the length (aka magnitude) of the XY as a vector, using the
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// Rounder to round to an int
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func (xy XY) Len(r Rounder) int {
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if xy[0] == 0 {
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return abs(xy[1])
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} else if xy[1] == 0 {
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return abs(xy[0])
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}
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xyf := xy.toF64()
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lf := math.Sqrt((xyf[0] * xyf[0]) + (xyf[1] * xyf[1]))
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return r.Round(lf)
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}
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// Add returns the result of adding the two XYs' fields individually
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func (xy XY) Add(xy2 XY) XY {
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xy[0] += xy2[0]
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xy[1] += xy2[1]
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return xy
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}
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// Mul returns the result of multiplying the two XYs' fields individually
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func (xy XY) Mul(xy2 XY) XY {
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xy[0] *= xy2[0]
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xy[1] *= xy2[1]
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return xy
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}
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// Div returns the results of dividing the two XYs' field individually, using
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// the Rounder to resolve floating results
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func (xy XY) Div(xy2 XY, r Rounder) XY {
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xyf, xy2f := xy.toF64(), xy2.toF64()
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return XY{
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r.Round(xyf[0] / xy2f[0]),
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r.Round(xyf[1] / xy2f[1]),
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}
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}
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// Scale returns the result of multiplying both of the XY's fields by the scalar
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func (xy XY) Scale(scalar int) XY {
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return xy.Mul(XY{scalar, scalar})
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}
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// Inv inverses the XY, a shortcut for xy.Scale(-1)
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func (xy XY) Inv() XY {
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return xy.Scale(-1)
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}
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// Sub subtracts xy2 from xy and returns the result. A shortcut for
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// xy.Add(xy2.Inv())
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func (xy XY) Sub(xy2 XY) XY {
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return xy.Add(xy2.Inv())
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}
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// Midpoint returns the midpoint between the two XYs. The rounder indicates what
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// to do about non-whole values when they're come across
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func (xy XY) Midpoint(xy2 XY, r Rounder) XY {
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return xy.Add(xy2.Sub(xy).Div(XY{2, 2}, r))
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}
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// Min returns an XY whose fields are the minimum values of the two XYs'
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// fields compared individually
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func (xy XY) Min(xy2 XY) XY {
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for i := range xy {
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if xy2[i] < xy[i] {
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xy[i] = xy2[i]
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}
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}
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return xy
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}
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// Max returns an XY whose fields are the Maximum values of the two XYs'
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// fields compared individually
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func (xy XY) Max(xy2 XY) XY {
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for i := range xy {
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if xy2[i] > xy[i] {
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xy[i] = xy2[i]
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}
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}
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return xy
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}
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