From f89c625f801fa6c0bf3e2423566249f6d483cd72 Mon Sep 17 00:00:00 2001
From: Daniel Slocombe <ds4314@ic.ac.uk>
Date: Wed, 21 Feb 2018 06:54:25 +0000
Subject: [PATCH] Add arrows for TikZ diagrams

---
 Text/LaTeX/Packages/TikZ/Simple.hs | 10 ++++++++++
 Text/LaTeX/Packages/TikZ/Syntax.hs | 11 +++++++++--
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/Text/LaTeX/Packages/TikZ/Simple.hs b/Text/LaTeX/Packages/TikZ/Simple.hs
index afac703..cff0f5e 100644
--- a/Text/LaTeX/Packages/TikZ/Simple.hs
+++ b/Text/LaTeX/Packages/TikZ/Simple.hs
@@ -54,6 +54,8 @@ type Point = (Double,Double)
 -- | A figure in the plane.
 data Figure =
    Line [Point] -- ^ Line along a list of points.
+ | Arrow [Point] -- ^ Line along a list of points with an arrowhead .
+ | Curvy [Point]
  | Polygon [Point] -- ^ Line along a list of points, but the last point will be joined
                    --   with the first one.
  | PolygonFilled [Point] -- ^ Same as 'Polygon', but the inner side will be filled with color.
@@ -79,10 +81,18 @@ castpoint (x,y) = T.pointAtXY x y
 radiansToDegrees :: Double -> Double
 radiansToDegrees x = (180 * x) / pi
 
+toTPoint :: Point -> T.TPoint
+toTPoint = uncurry T.pointAtXY
+
 -- | Translate a 'Figure' to a 'TikZ' script.
 figuretikz :: Figure -> TikZ
 figuretikz (Line []) = emptytikz
 figuretikz (Line (p:ps)) = T.draw $ foldl (\y x -> y T.->- castpoint x) (T.Start $ castpoint p) ps
+figuretikz (Arrow []) = emptytikz
+figuretikz (Arrow (p:ps)) = T.path [T.Draw, T.Arrow] $ foldl (\y x -> y T.->- castpoint x) (T.Start $ castpoint p) ps
+figuretikz (Curvy []) = emptytikz
+--figuretikz (Curvy (p:ps)) = T.path [T.Draw, T.Smooth] $ foldl (\y x -> y T.->- castpoint x) (T.Start $ castpoint p) ps
+figuretikz (Curvy (ps)) = T.Curvy (toTPoint <$> ps)
 figuretikz (Polygon []) = emptytikz
 figuretikz (Polygon (p:ps)) = T.draw $ T.Cycle $ foldl (\y x -> y T.->- castpoint x) (T.Start $ castpoint p) ps
 figuretikz (PolygonFilled []) = emptytikz
diff --git a/Text/LaTeX/Packages/TikZ/Syntax.hs b/Text/LaTeX/Packages/TikZ/Syntax.hs
index 5d432b0..01d42d1 100644
--- a/Text/LaTeX/Packages/TikZ/Syntax.hs
+++ b/Text/LaTeX/Packages/TikZ/Syntax.hs
@@ -31,7 +31,7 @@ module Text.LaTeX.Packages.TikZ.Syntax (
   , Color (..)
   , Word8
     -- * TikZ
-  , TikZ
+  , TikZ (..)
   , emptytikz
   , path
   , scope
@@ -245,13 +245,14 @@ instance Render Parameter where
 -- | A Ti/k/Z script.
 data TikZ =
     PathAction [ActionType] TPath
+  | Curvy [TPoint]
   | Scope [Parameter] TikZ
   | TikZSeq (S.Seq TikZ)
     deriving Show
 
 -- | Different types of actions that can be performed
 --   with a 'TPath'. See 'path' for more information.
-data ActionType = Draw | Fill | Clip | Shade deriving Show
+data ActionType = Draw | Fill | Clip | Shade | Arrow deriving Show
 
 -- | Just an empty script.
 emptytikz :: TikZ
@@ -259,14 +260,20 @@ emptytikz = TikZSeq mempty
 
 instance Render TikZ where
  render (PathAction ts p) = "\\path" <> render ts <> " " <> render p <> " ; "
+ render (Curvy ps) = "\\draw[->] plot [smooth] coordinates { " <> (renderPoints ps) <> " } ; "
  render (Scope ps t) = "\\begin{scope}" <> render ps <> render t <> "\\end{scope}"
  render (TikZSeq ts) = foldMap render ts
 
+renderPoints :: [TPoint] -> Text
+renderPoints [] = ""
+renderPoints (p:ps) = render p <> " " <> renderPoints ps
+
 instance Render ActionType where
  render Draw  = "draw"
  render Fill  = "fill"
  render Clip  = "clip"
  render Shade = "shade"
+ render Arrow = "->"
 
 -- | A path can be used in different ways.
 --