feat: Turtle.Polygon() partial support ( Fixes #194 )

Author: StartAutomating

Types/Turtle/Polygon.ps1

@@ -1,10 +1,51 @@
+<#
+.SYNOPSIS
+    Draws a polygon
+.DESCRIPTION
+    Draws a regular polygon with N sides.
+
+    To draw a closed polygon, provide a whole number of sides.
+
+    To draw an open polygon, provide a fractial number of sides.
+.EXAMPLE
+    turtle polygon 42 3
+.EXAMPLE
+    turtle polygon 42 4
+.EXAMPLE
+    turtle polygon 42 6
+.EXAMPLE
+    turtle polygon 42 8
+.EXAMPLE
+    turtle polygon 42 3.75
+.EXAMPLE
+    turtle polygon 42 3.001 morph @(
+        turtle polygon 42 3.001
+        turtle polygon 42 4
+        turtle polygon 42 3.001
+    ) save ./TriangleToSquare.svg 
+
+#>
 param(
-    $Size = 100, 
-    $SideCount = 6
+# The default size of each segment of the polygon
+[double]$Size = 42,
+# The number of sides in the polygon.  
+# If this is not a whole number, the polygon will not be closed.
+[double]$SideCount = 6
 )
 
-$null = foreach ($n in 1..$SideCount) {    
-    $this.Forward($Size)
-    $this.Rotate(360 / $SideCount)    
+# Determine the absolute side count
+$absSideCount = [Math]::Abs($SideCount)
+# and, for each whole number between 1 and that side count
+$null = foreach ($n in 1..([Math]::Floor($absSideCount))) {
+    # Rotate and move forward
+    $this.Rotate(360 / $SideCount).Forward($Size)    
 }
-return $this
+# Determine if there was a remainder
+$remainder = $SideCount - [Math]::Floor($SideCount)
+# If there was not, return this polygon
+if (-not $remainder) { return $this }
+# Otherwise, we do one more partial rotation (multiplied by the remainder)
+# and draw one more line segment (multiplied by the remainder)
+# (the effect will be like watching a polygon close)
+return $this.Rotate((360 / $SideCount) * $remainder).Forward($remainder * $Size)
+