Add Gosper curve fractal implementation

fractals/gosper_curve.py

@@ -0,0 +1,89 @@
+"""
+Description
+The Gosper curve (also known as the flowsnake) is a fractal curve discovered
+by Bill Gosper. It is generated recursively by replacing each line segment
+with a specific pattern of smaller segments rotated by multiples of
+60 degrees.
+
+```
+With each iteration, the curve becomes more complex and gradually fills
+a hexagonal region.
+
+(description adapted from https://en.wikipedia.org/wiki/Gosper_curve)
+```
+
+Requirements (pip):
+- turtle (standard library)
+"""
+
+import math
+import turtle
+
+def draw_gosper_curve(
+side_length: float, depth: int, direction: int = -1, angle: float = 60.0
+) -> None:
+"""
+Recursively draw a Gosper curve using turtle graphics.
+
+```
+Args:
+    side_length: Length of the current segment.
+    depth: Recursive depth of the fractal.
+    direction: Direction of the curve (1 or -1).
+    angle: Turn angle in degrees.
+
+>>> import turtle
+>>> draw_gosper_curve(100.0, 1)
+"""
+if depth == 0:
+    turtle.forward(side_length)
+    return
+
+side_length /= math.sqrt(7)
+depth -= 1
+
+if direction == -1:
+    draw_gosper_curve(side_length, depth, -1, angle)
+    turtle.left(angle)
+    draw_gosper_curve(side_length, depth, 1, angle)
+    turtle.left(2 * angle)
+    draw_gosper_curve(side_length, depth, 1, angle)
+    turtle.right(angle)
+    draw_gosper_curve(side_length, depth, -1, angle)
+    turtle.right(2 * angle)
+    draw_gosper_curve(side_length, depth, -1, angle)
+    draw_gosper_curve(side_length, depth, -1, angle)
+    turtle.right(angle)
+    draw_gosper_curve(side_length, depth, 1, angle)
+    turtle.left(angle)
+else:
+    turtle.right(angle)
+    draw_gosper_curve(side_length, depth, -1, angle)
+    turtle.left(angle)
+    draw_gosper_curve(side_length, depth, 1, angle)
+    draw_gosper_curve(side_length, depth, 1, angle)
+    turtle.left(2 * angle)
+    draw_gosper_curve(side_length, depth, 1, angle)
+    turtle.left(angle)
+    draw_gosper_curve(side_length, depth, -1, angle)
+    turtle.right(2 * angle)
+    draw_gosper_curve(side_length, depth, -1, angle)
+    turtle.right(angle)
+    draw_gosper_curve(side_length, depth, 1, angle)
+```
+
+if **name** == "**main**":
+turtle.title("Gosper Curve")
+turtle.speed(0)
+
+```
+turtle.penup()
+turtle.goto(0, -200)
+turtle.pendown()
+
+draw_gosper_curve(200.0, 4)
+
+turtle.exitonclick()
+```
+
+"""