From e01e4790402204af02ab0127ef5b633fb7748cd4 Mon Sep 17 00:00:00 2001
From: Dominic Steinitz <dominic@steinitz.org>
Date: Sat, 16 May 2015 12:32:23 +0100
Subject: Handle inline math with mathjax.

---
 haddock-library/src/Documentation/Haddock/Parser.hs | 16 +++++++++++++++-
 haddock-library/src/Documentation/Haddock/Types.hs  |  1 +
 2 files changed, 16 insertions(+), 1 deletion(-)

(limited to 'haddock-library/src/Documentation/Haddock')

diff --git a/haddock-library/src/Documentation/Haddock/Parser.hs b/haddock-library/src/Documentation/Haddock/Parser.hs
index ca9e9d8d..919ea37f 100644
--- a/haddock-library/src/Documentation/Haddock/Parser.hs
+++ b/haddock-library/src/Documentation/Haddock/Parser.hs
@@ -73,6 +73,7 @@ overIdentifier f d = g d
     g (DocCodeBlock x) = DocCodeBlock $ g x
     g (DocHyperlink x) = DocHyperlink x
     g (DocPic x) = DocPic x
+    g (DocMathInline x) = DocMathInline x
     g (DocAName x) = DocAName x
     g (DocProperty x) = DocProperty x
     g (DocExamples x) = DocExamples x
@@ -113,7 +114,8 @@ parseStringBS = snd . parse p
   where
     p :: Parser (DocH mod Identifier)
     p = docConcat <$> many (monospace <|> anchor <|> identifier <|> moduleName
-                            <|> picture <|> markdownImage <|> hyperlink <|> bold
+                            <|> picture <|> mathDisplay <|> markdownImage
+                            <|> hyperlink <|> bold
                             <|> emphasis <|> encodedChar <|> string'
                             <|> skipSpecialChar)
 
@@ -224,6 +226,18 @@ picture :: Parser (DocH mod a)
 picture = DocPic . makeLabeled Picture . decodeUtf8
           <$> disallowNewline ("<<" *> takeUntil ">>")
 
+-- FIXME: I have just copied the code for `picture` but it is not
+-- clear why we should disallow a newline (if that is what
+-- `disallowNewline` does)
+
+-- | Inline math parser, surrounded by \$\$ and \$\$.
+--
+-- >>> parseString "$$\int_{-infty}^{infty} e^{-x^2/2} = \sqrt{2\pi}$$"
+-- DocMathInline (DocString "\int_{-infty}^{infty} e^{-x^2/2} = \sqrt{2\pi}")
+mathDisplay :: Parser (DocH mod a)
+mathDisplay = DocMathInline . decodeUtf8
+              <$> disallowNewline  ("$$" *> takeUntil "$$")
+
 markdownImage :: Parser (DocH mod a)
 markdownImage = fromHyperlink <$> ("!" *> linkParser)
   where
diff --git a/haddock-library/src/Documentation/Haddock/Types.hs b/haddock-library/src/Documentation/Haddock/Types.hs
index 4ef89658..2b1e7f26 100644
--- a/haddock-library/src/Documentation/Haddock/Types.hs
+++ b/haddock-library/src/Documentation/Haddock/Types.hs
@@ -71,6 +71,7 @@ data DocH mod id
   | DocCodeBlock (DocH mod id)
   | DocHyperlink Hyperlink
   | DocPic Picture
+  | DocMathInline String
   | DocAName String
   | DocProperty String
   | DocExamples [Example]
-- 
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