From 85b4f603d3c27e56766689d7c52f5b2ddf35a3a5 Mon Sep 17 00:00:00 2001
From: Kei Hibino <ex8k.hibino@gmail.com>
Date: Mon, 10 Jun 2013 20:10:54 +0900
Subject: [PATCH] Add document of class method.

---
 relational-join/src/Database/Relational/Query/Expr.hs | 1 +
 1 file changed, 1 insertion(+)

diff --git a/relational-join/src/Database/Relational/Query/Expr.hs b/relational-join/src/Database/Relational/Query/Expr.hs
index ef96cbad..4d4deb74 100644
--- a/relational-join/src/Database/Relational/Query/Expr.hs
+++ b/relational-join/src/Database/Relational/Query/Expr.hs
@@ -56,6 +56,7 @@ stringExprSQL =  ('\'':) . (++ "'") . escapeStringToSqlExpr
 
 -- | Interface for constant SQL expression.
 class ShowConstantSQL a where
+  -- | Make constant SQL expression 'String' from Haskell type 'a'.
   showConstantSQL :: a -> String
 
 -- | Constant SQL expression of 'Int16'.