From 9a0b116cd7a78590cd46bb17bbd542d93de2acef Mon Sep 17 00:00:00 2001
From: defanor <defanor@uberspace.net>
Date: Sat, 16 Dec 2017 18:39:15 +0300
Subject: Add the 'handleRecCon' function

Abstract the code with it.
---
 Coalpit.hs    | 44 +++++++++++++++++++-------------------------
 coalpit.cabal | 11 ++++++-----
 2 files changed, 25 insertions(+), 30 deletions(-)

diff --git a/Coalpit.hs b/Coalpit.hs
index b4b7b2f..42fb1ae 100644
--- a/Coalpit.hs
+++ b/Coalpit.hs
@@ -171,6 +171,21 @@ instance (GCoalpit a, GCoalpit b) => GCoalpit (a :*: b) where
 
 -- Sums
 
+-- | Handles recursive constructors.
+handleRecCon :: GCoalpit a
+             => String
+             -- ^ Constructor name
+             -> Options
+             -> [String]
+             -> Proxy (a p)
+             -> String
+handleRecCon nameA opt path (Proxy :: Proxy (a p)) = conNameMod opt nameA
+  ++ if nameA `elem` path
+     then "..."
+     else case gArgHelper opt (nameA : path) (Proxy :: Proxy (a p)) of
+            "" -> ""
+            s -> ' ' : s
+
 instance (Constructor conA, GCoalpit a, GCoalpit (b :+: c)) =>
   GCoalpit ((b :+: c) :+: C1 conA a) where
   gArgParser opt =
@@ -185,14 +200,9 @@ instance (Constructor conA, GCoalpit a, GCoalpit (b :+: c)) =>
     in concat [ "("
               , gArgHelper opt path (Proxy :: Proxy ((b :+: c) p))
               , " | "
-              , conNameMod opt nameA
-              , if nameA `elem` path
-                then "..."
-                else spaceNonEmpty $
-                     gArgHelper opt (nameA : path) (Proxy :: Proxy (a p))
+              , handleRecCon nameA opt path (Proxy :: Proxy (a p))
               , ")"]
 
-
 instance (Constructor conA, GCoalpit a, GCoalpit (b :+: c)) =>
   GCoalpit (C1 conA a :+: (b :+: c)) where
   gArgParser opt =
@@ -205,11 +215,7 @@ instance (Constructor conA, GCoalpit a, GCoalpit (b :+: c)) =>
   gArgHelper opt path (Proxy :: Proxy ((C1 conA a :+: (b :+: c)) p)) =
     let nameA = conName (undefined :: C1 conA a p)
     in concat [ "("
-              , conNameMod opt nameA
-              , if nameA `elem` path
-                then "..."
-                else spaceNonEmpty $
-                     gArgHelper opt (nameA : path) (Proxy :: Proxy (a p))
+              , handleRecCon nameA opt path (Proxy :: Proxy (a p))
               , " | "
               , gArgHelper opt path (Proxy :: Proxy ((b :+: c) p))
               , ")"]
@@ -230,23 +236,11 @@ instance (Constructor conA, Constructor conB, GCoalpit a, GCoalpit b) =>
     let nameA = conName (undefined :: C1 conA a p)
         nameB = conName (undefined :: C1 conB b p)
     in concat [ "("
-              , conNameMod opt nameA
-              , if nameA `elem` path
-                then "..."
-                else spaceNonEmpty $
-                     gArgHelper opt (nameA : path) (Proxy :: Proxy (a p))
+              , handleRecCon nameA opt path (Proxy :: Proxy (a p))
               , " | "
-              , conNameMod opt nameB
-              , if nameB `elem` path
-                then "..."
-                else spaceNonEmpty $
-                     gArgHelper opt (nameB : path) (Proxy :: Proxy (b p))
+              , handleRecCon nameB opt path (Proxy :: Proxy (b p))
               , ")"]
 
-spaceNonEmpty :: String -> String
-spaceNonEmpty "" = ""
-spaceNonEmpty s = ' ' : s
-
 
 -- Record Selectors
 
diff --git a/coalpit.cabal b/coalpit.cabal
index 38e8518..51507e0 100644
--- a/coalpit.cabal
+++ b/coalpit.cabal
@@ -1,11 +1,12 @@
 name:                coalpit
 version:             0.1.0.2
 synopsis:            Command-line options parsing and printing
-description:         This library generates parsers and printers for given
-                     data types, in the form of command-line arguments -- so
-                     that they can be used to quickly get program interfaces via
-                     a shared library, while being suitable for scripting and as
-                     user interfaces.
+description:         This library generates parsers and printers for
+                     given data types, in the form of command-line
+                     arguments – so that they can be used to quickly
+                     get program interfaces via a shared library,
+                     while being suitable for scripting and as user
+                     interfaces.
 license:             BSD3
 license-file:        LICENSE
 author:              defanor
-- 
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