Fixed merge issue with c code, modified angle function

chapters/computational_geometry/gift_wrapping/graham_scan/code/haskell/grahamScan.hs

@@ -3,27 +3,18 @@ import Data.Function (on)
 
 type Point = (Double, Double)
 
-angle :: Point -> Point -> Point -> Double
-angle a@(xa, ya) b@(xb, yb) c@(xc, yc)
- | a==b || c==b = 0
- | theta<0 = theta+2*pi
- | otherwise = theta
- where thetaA = atan2 (ya-yb) (xa-xb)
- thetaC = atan2 (yc-yb) (xc-xb)
- theta = thetaC - thetaA
-
 ccw :: Point -> Point -> Point -> Double
 ccw (xa, ya) (xb, yb) (xc, yc) = (xb - xa) * (yc - ya) - (yb - ya) * (xc - xa)
 
 grahamScan :: [Point] -> [Point]
 grahamScan [] = []
 grahamScan pts = wrap sortedPts [p0]
  where p0@(x, y)= minimumBy (compare `on` snd) pts
- sortedPts = init $ sortOn (negate . angle (x, y-1) p0) pts
- wrap [] p = p
+ sortedPts = sortOn (\(px, py) -> atan2 (py-y) (px-x) ) $ filter (/=p0) pts
+ wrap [] ps = ps
  wrap (s:ss) [p] = wrap ss [s, p]
  wrap (s:ss) (p1:p2:ps)
- | ccw s p1 p2 < 0 = wrap (s:ss) (p2:ps)
+ | ccw s p1 p2 > 0 = wrap (s:ss) (p2:ps)
  | otherwise = wrap ss (s:p1:p2:ps)
 
 main = do

chapters/computational_geometry/gift_wrapping/graham_scan/graham_scan.md

@@ -15,7 +15,9 @@ We can find whether a rotation is counter-clockwise with trigonometric functions
 {% sample lang="jl" %}
 [import:30-32, lang:"julia"](code/julia/graham.jl)
 {% sample lang="hs" %}
-[import:15-16, lang:"haskell"](code/haskell/grahamScan.hs)
+[import:6-7, lang:"haskell"](code/haskell/grahamScan.hs)
+{% sample lang="c" %}
+[import:24-26, lang:"c_cpp"](code/c/graham.c)
 {% endmethod %}
 
 If the output of this function is 0, the points are collinear.
@@ -33,7 +35,9 @@ In the end, the code should look something like this:
 {% sample lang="jl" %}
 [import:34-69, lang:"julia"](code/julia/graham.jl)
 {% sample lang="hs" %}
-[import:18-27, lang:"haskell"](code/haskell/grahamScan.hs)
+[import:9-18, lang:"haskell"](code/haskell/grahamScan.hs)
+{% sample lang="c" %}
+[import:65-95, lang:"c_cpp"](code/c/graham.c)
 {% endmethod %}
 
 ### Bibliography
@@ -49,6 +53,8 @@ In the end, the code should look something like this:
 {% sample lang="hs" %}
 ### Haskell
 [import, lang:"haskell"](code/haskell/grahamScan.hs)
+{% sample lang="c" %}
+[import, lang:"c_cpp"](code/c/graham.c)
 {% endmethod %}
 
 <script>