Trees implemented. There is not monad version yet.

HaTeX.cabal

@@ -69,6 +69,9 @@ Library
           Text.LaTeX.Packages.Color.Monad
         Text.LaTeX.Packages.Graphicx
           Text.LaTeX.Packages.Graphicx.Monad
+        -- Trees
+        Text.LaTeX.Packages.Trees
+          Text.LaTeX.Packages.Trees.Qtree
   Extensions: GeneralizedNewtypeDeriving
             , OverloadedStrings
             , CPP

Text/LaTeX/Base.hs

@@ -43,5 +43,5 @@ instance Num LaTeX where
  negate = (TeXEmpty -)
  fromInteger = TeXRaw . fromString . show
  -- Non-defined methods
- abs _    = "Cannot use \"abs\" Num method with a LaTeX value."
- signum _ = "Cannot use \"signum\" Num method with a LaTeX value."
+ abs _    = error "Cannot use \"abs\" Num method with a LaTeX value."
+ signum _ = error "Cannot use \"signum\" Num method with a LaTeX value."

Text/LaTeX/Packages/Trees.hs

@@ -0,0 +1,10 @@
+
+module Text.LaTeX.Packages.Trees (
+  -- * Tree
+  Tree (..)
+ ) where
+
+-- | Tree datatype.
+data Tree a =
+   Leaf a -- ^ Leafs are non-empty.
+ | Node (Maybe a) [Tree a] -- ^ Node values are optional.

Text/LaTeX/Packages/Trees/Qtree.hs

@@ -0,0 +1,31 @@
+
+{-# LANGUAGE OverloadedStrings #-}
+
+module Text.LaTeX.Packages.Trees.Qtree (
+    -- * Tree to LaTeX rendering
+    tree
+  , rendertree
+  ) where
+
+import Text.LaTeX.Base
+import Text.LaTeX.Base.Syntax
+import Text.LaTeX.Packages.Trees
+--
+import Data.Monoid
+import Data.List (intersperse)
+
+tree_ :: (a -> LaTeX) -> Tree a -> LaTeX
+tree_ f (Leaf x) = braces $ f x
+tree_ f (Node mx ts) =
+  mconcat [ "["
+          , maybe mempty (("." <>) . braces . f) mx
+          , " "
+          , mconcat $ intersperse " " $ fmap (tree_ f) ts
+          , " ]"
+            ]
+
+tree :: (a -> LaTeX) -> Tree a -> LaTeX
+tree f t = TeXCommS "Tree" <> " " <> tree_ f t
+
+rendertree :: Render a => Tree a -> LaTeX
+rendertree = tree rendertex