From 19eed1744b87d97ad6f65bd2a2215febc35d0982 Mon Sep 17 00:00:00 2001
From: Paolo Capriotti <p.capriotti@gmail.com>
Date: Wed, 30 Jul 2014 19:15:57 +0100
Subject: [PATCH] Add `Show` instance for `ParserResult` (fixes #95).

---
 CHANGELOG.md                 |  2 ++
 Options/Applicative/Types.hs | 11 +++++++++++
 2 files changed, 13 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c2104035..6b80fa53 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,8 @@
 
 - Added low-level function to handle parse results (pull request \#94).
 
+- `ParserResult` now has a `Show` instance (see issue \#95).
+
 - Fixed bugs
     * \#93 - Formatting problem for several sub-parsers
 
diff --git a/Options/Applicative/Types.hs b/Options/Applicative/Types.hs
index 370fbf9b..7d2fa53e 100644
--- a/Options/Applicative/Types.hs
+++ b/Options/Applicative/Types.hs
@@ -236,14 +236,25 @@ instance Monoid Completer where
 newtype CompletionResult = CompletionResult
   { execCompletion :: String -> IO String }
 
+instance Show CompletionResult where
+  showsPrec p _ = showParen (p > 10) $
+    showString "CompletionResult _"
+
 newtype ParserFailure = ParserFailure
   { execFailure :: String -> (String, ExitCode) }
 
+instance Show ParserFailure where
+  showsPrec p (ParserFailure f)
+    = showParen (p > 10)
+    $ showString "ParserFailure "
+    . showsPrec 11 (f "<program>")
+
 -- | Result of 'execParserPure'.
 data ParserResult a
   = Success a
   | Failure ParserFailure
   | CompletionInvoked CompletionResult
+  deriving Show
 
 type Args = [String]