created rectangle struct and IsRect()

defined what a rectangle is and also implemented IsRect(), which returns
a bool whether the coordinates given make a rectangle or not.  Tests
were written for IsRect()

cmd/recty/main.go

@@ -0,0 +1,31 @@
+package main
+
+import (
+	"fmt"
+
+	"s.mcquay.me/dm/rect"
+)
+
+func main() {
+	r := rect.Rectangle{
+		P1: rect.Point{1, 1},
+		P2: rect.Point{1, 2},
+		P3: rect.Point{2, 1},
+		P4: rect.Point{2, 2},
+	}
+	fmt.Println(r.IsRect())
+	r1 := rect.Rectangle{
+		P1: rect.Point{0, 0},
+		P2: rect.Point{0, 1},
+		P3: rect.Point{1, 0},
+		P4: rect.Point{1, 1},
+	}
+	fmt.Println(r1.IsRect())
+	r1 := rect.Rectangle{
+		P1: rect.Point{0, 0},
+		P2: rect.Point{0, 1},
+		P3: rect.Point{1, 0},
+		P4: rect.Point{1, 1},
+	}
+	fmt.Println(r1.IsRect())
+}

point.go

@@ -0,0 +1,5 @@
+package rect
+
+type Point struct {
+	X, Y float64
+}

rectangle.go

@@ -0,0 +1,24 @@
+package rect
+
+import "math"
+
+type Rectangle struct {
+	P1, P2, P3, P4 Point
+}
+
+func (r Rectangle) IsRect() bool {
+	// make sure they aren't all just the same point
+	if (r.P1.X == r.P2.X && r.P1.X == r.P3.X && r.P1.X == r.P4.X) &&
+		(r.P1.Y == r.P2.Y && r.P1.Y == r.P3.Y && r.P1.Y == r.P4.Y) {
+		return false
+	}
+
+	cx := (r.P1.X + r.P2.X + r.P3.X + r.P4.X) / 4.0
+	cy := (r.P1.Y + r.P2.Y + r.P3.Y + r.P4.Y) / 4.0
+
+	dd1 := math.Sqrt(math.Abs(cx-r.P1.X)) + math.Sqrt(math.Abs(cy-r.P1.Y))
+	dd2 := math.Sqrt(math.Abs(cx-r.P2.X)) + math.Sqrt(math.Abs(cy-r.P2.Y))
+	dd3 := math.Sqrt(math.Abs(cx-r.P3.X)) + math.Sqrt(math.Abs(cy-r.P3.Y))
+	dd4 := math.Sqrt(math.Abs(cx-r.P4.X)) + math.Sqrt(math.Abs(cy-r.P4.Y))
+	return dd1 == dd2 && dd1 == dd3 && dd1 == dd4
+}

rectangle_test.go

@@ -0,0 +1,29 @@
+package rect
+
+import "testing"
+
+func TestIsRect(t *testing.T) {
+	var isRectTests = []struct {
+		r        Rectangle
+		expected bool
+	}{
+		{Rectangle{P1: Point{1, 1}, P2: Point{1, 2}, P3: Point{2, 1}, P4: Point{2, 2}}, true},
+		{Rectangle{P1: Point{0, 0}, P2: Point{0, 1}, P3: Point{1, 0}, P4: Point{1, 1}}, true},
+		{Rectangle{P1: Point{0, 0}, P2: Point{0, -1}, P3: Point{-1, 0}, P4: Point{-1, -1}}, true},
+		{Rectangle{P1: Point{1.5, 1.5}, P2: Point{1.5, 3.5}, P3: Point{3.5, 1.5}, P4: Point{3.5, 3.5}}, true},
+		{Rectangle{P1: Point{0, 0}, P2: Point{0, 3}, P3: Point{2, 0}, P4: Point{2, 3}}, true},
+		{Rectangle{P1: Point{0, 0}, P2: Point{0, 100}, P3: Point{-1, 0}, P4: Point{0, 23}}, false},
+		{Rectangle{P1: Point{0, 0}, P2: Point{0, 0}, P3: Point{0, 0}, P4: Point{0, 0}}, false},
+	}
+	for _, rt := range isRectTests {
+		actual := rt.r.IsRect()
+		if actual != rt.expected {
+			t.Errorf(
+				"failed spiral:\n\texpected: %d\n\t  actual: %d",
+				rt.expected,
+				actual,
+			)
+		}
+
+	}
+}