From edd4ec38d73b5a2256cc2ced4eb6ba664151baab Mon Sep 17 00:00:00 2001
From: hasufell <hasufell@hasufell.de>
Date: Thu, 8 Jan 2015 01:41:14 +0100
Subject: [PATCH] POLYGON: add polygon module

---
 Algebra/Polygon.hs | 26 ++++++++++++++++++++++++++
 CG2.cabal          |  9 ++++++---
 2 files changed, 32 insertions(+), 3 deletions(-)
 create mode 100644 Algebra/Polygon.hs

diff --git a/Algebra/Polygon.hs b/Algebra/Polygon.hs
new file mode 100644
index 0000000..46f629e
--- /dev/null
+++ b/Algebra/Polygon.hs
@@ -0,0 +1,26 @@
+{-# OPTIONS_HADDOCK ignore-exports #-}
+
+module Algebra.Polygon where
+
+import Algebra.Vector
+import MyPrelude
+{- import Diagrams.Coordinates -}
+
+
+splitPoly :: [PT]
+          -> Segment
+          -> [[PT]]
+splitPoly pts (a, b)
+  | elem a pts && elem b pts =
+    [b : takeWhile (/= b) shiftedPoly, a : dropWhile (/= b) shiftedPoly]
+  | otherwise = [[]]
+    where
+      shiftedPoly = shiftM' a pts
+
+
+polySegments :: [PT] -> [Segment]
+polySegments p@(x':_:_:_) = go p ++ [(last p, x')]
+  where
+    go (x:y:xs) = (x, y) : go (y:xs)
+    go _        = []
+polySegments _ = []
diff --git a/CG2.cabal b/CG2.cabal
index 6b580f3..99400e4 100644
--- a/CG2.cabal
+++ b/CG2.cabal
@@ -54,7 +54,8 @@ executable Gtk
   main-is:             GtkMain.hs
 
   -- Modules included in this executable, other than Main.
-  other-modules:       Algebra.Vector
+  other-modules:       Algebra.Polygon
+                       Algebra.Vector
                        Algorithms.GrahamScan
                        Algorithms.PolygonIntersection
                        Algorithms.PolygonTriangulation
@@ -103,7 +104,8 @@ executable Gif
   main-is:             GifMain.hs
 
   -- Modules included in this executable, other than Main.
-  other-modules:       Algebra.Vector
+  other-modules:       Algebra.Polygon
+                       Algebra.Vector
                        Algorithms.GrahamScan
                        Algorithms.PolygonIntersection
                        Algorithms.PolygonTriangulation
@@ -149,7 +151,8 @@ executable Test
   main-is:             TestMain.hs
 
   -- Modules included in this executable, other than Main.
-  other-modules:       Algebra.Vector
+  other-modules:       Algebra.Polygon
+                       Algebra.Vector
                        Algorithms.GrahamScan
                        Algorithms.PolygonIntersection
                        Algorithms.PolygonTriangulation