Add trigram function and test script

test_trigram.py

@@ -0,0 +1,12 @@
+from turtle import left
+from trigram import (
+    draw_trigram, 
+    건, 
+    곤,
+    리,
+    감,
+)
+
+left(90)
+draw_trigram(리, 200)
+input()

trigram.py

@@ -0,0 +1,56 @@
+from turtle import *
+
+건 = [True, True, True]
+곤 = [False, False, False]
+리 = [True, False, True]
+감 = [False, True, False]
+
+def draw_trigram(pattern, width):
+    """Draws a trigram from the Korean flag. 
+    The starting and ending point is the center of the bottom of 
+    the trigram, with the turtle facing up.
+    The pattern should be a list of True/False values, indicating
+    whether each bar should be solid, starting from the top.
+    """
+    unit = width/12
+    for bar_type in pattern:
+        draw_trigram_bar(bar_type, width)
+        fly(unit * 3)
+    fly(unit*-9)
+
+def draw_trigram_bar(is_solid, width):
+    """Draws a single bar from a trigram, starting and ending at the center 
+    of the bottom of the bar.
+    """
+    unit = width/12
+    right(90)
+    fly(unit*-6)
+    if is_solid:
+        draw_black_rectangle(unit*12, unit*2)
+        fly(width/2)
+    else:
+        draw_black_rectangle(unit*5.5, unit*2)
+        fly(unit*6.5)
+        draw_black_rectangle(unit*5.5, unit*2)
+        fly(unit*-0.5)
+    left(90)
+
+def draw_black_rectangle(width, height):
+    """Draws a filled black rectangle, starting and ending at the bottom 
+    left corner and turning to the left.
+    """
+    color('black')
+    fillcolor('black')
+    begin_fill()
+    for half in range(2):
+        forward(width)
+        left(90)
+        forward(height)
+        left(90)
+    end_fill()
+
+def fly(steps):
+    "Move without drawing"
+    penup()
+    forward(steps)
+    pendown()