feat: Turtle.SierpinskiArrowheadCurve ( Fixes #40 )

Author: James Brundage

Types/Turtle/SierpinskiArrowheadCurve.ps1

@@ -0,0 +1,36 @@
+<#
+.SYNOPSIS
+    Generates a Sierpinski Arrowhead Curve.
+.DESCRIPTION
+    Generates a Sierpinski Arrowhead Curve using turtle graphics.
+.LINK
+    https://en.wikipedia.org/wiki/Sierpi%C5%84ski_curve#Representation_as_Lindenmayer_system_2
+.EXAMPLE
+    $turtle.SierpinskiArrowheadCurve().Pattern.Save("$pwd/SierpinskiArrowhead.svg")
+.EXAMPLE
+    $turtle.Clear()
+    $turtle.SierpinskiArrowheadCurve(10,4)
+    $turtle.PatternTransform = @{
+        'scale' = 0.9        
+    }    
+    $turtle.PatternAnimation = "
+    <animateTransform attributeName='patternTransform' attributeType='XML' type='scale' values='1;0.9;1' dur='19s' repeatCount='indefinite' additive='sum' />
+    <animateTransform attributeName='patternTransform' attributeType='XML' type='skewY' values='0;-30;30;-30;0' dur='67s' repeatCount='indefinite' additive='sum' />
+    <animateTransform attributeName='patternTransform' attributeType='XML' type='skewX' values='0;-30;30;-30;0' dur='83s' repeatCount='indefinite' additive='sum' />
+    "
+    $turtle.Pattern.Save("$pwd/SierpinskiArrowhead2.svg")
+#>
+
+param(
+    [double]$Size = 30,
+    [int]$Order = 8,
+    [double]$Angle = 60
+)
+return $this.L('XF',  [Ordered]@{
+    X = 'YF + XF + Y'
+    Y = 'XF - YF - X'
+}, $Order, [Ordered]@{
+    '\+'    = { $this.Rotate($Angle)        }
+    '-'     = { $this.Rotate($Angle * -1)   }
+    'F'     = { $this.Forward($Size)        }
+})