Fix handling of Char literals

Fixes cdepillabout#45.

src/Text/Pretty/Simple/Internal/Expr.hs

@@ -36,6 +36,7 @@ data Expr
   | Braces !(CommaSeparated [Expr])
   | Parens !(CommaSeparated [Expr])
   | StringLit !String
+  | CharLit !String
   | NumberLit !String
   -- ^ We could store this as a 'Rational', say, instead of a 'String'.
   -- However, we will never need to use its value for anything. Indeed, the

src/Text/Pretty/Simple/Internal/ExprParser.hs

@@ -39,6 +39,7 @@ parseExpr ('(':rest) = first (Parens . CommaSeparated) $ parseCSep ')' rest
 parseExpr ('[':rest) = first (Brackets . CommaSeparated) $ parseCSep ']' rest
 parseExpr ('{':rest) = first (Braces . CommaSeparated) $ parseCSep '}' rest
 parseExpr ('"':rest) = first StringLit $ parseStringLit rest
+parseExpr ('\'':rest) = first CharLit $ parseCharLit rest
 parseExpr (c:rest) | isDigit c = first NumberLit $ parseNumberLit c rest
 parseExpr other      = first Other $ parseOther other
 
@@ -48,6 +49,8 @@ parseExpr other      = first Other $ parseOther other
 --
 -- >>> parseExprs $ "Foo \"hello \\\"world!\""
 -- ([Other "Foo ",StringLit "hello \\\"world!"],"")
+-- >>> parseExprs $ "'\\''"
+-- ([CharLit "\\'"],"")
 parseExprs :: String -> ([Expr], String)
 parseExprs [] = ([], "")
 parseExprs s@(c:_)
@@ -76,6 +79,14 @@ parseStringLit ('\\':c:cs) = ('\\':c:cs', rest)
 parseStringLit (c:cs) = (c:cs', rest)
   where (cs', rest) = parseStringLit cs
 
+parseCharLit :: String -> (String, String)
+parseCharLit [] = ("", "")
+parseCharLit ('\'':rest) = ("", rest)
+parseCharLit ('\\':c:cs) = ('\\':c:cs', rest)
+  where (cs', rest) = parseCharLit cs
+parseCharLit (c:cs) = (c:cs', rest)
+  where (cs', rest) = parseCharLit cs
+
 -- | Parses integers and reals, like @123@ and @45.67@.
 --
 -- To be more precise, any numbers matching the regex @\\d+(\\.\\d+)?@ should

src/Text/Pretty/Simple/Internal/ExprToOutput.hs

@@ -227,6 +227,10 @@ putExpression (StringLit string) = do
   nest <- gets nestLevel
   when (nest < 0) $ addToNestLevel 1
   addOutputs [OutputStringLit string, OutputOther " "]
+putExpression (CharLit string) = do
+  nest <- gets nestLevel
+  when (nest < 0) $ addToNestLevel 1
+  addOutputs [OutputCharLit string, OutputOther " "]
 putExpression (NumberLit integer) = do
   nest <- gets nestLevel
   when (nest < 0) $ addToNestLevel 1

src/Text/Pretty/Simple/Internal/Output.hs

@@ -70,6 +70,8 @@ data OutputType
   -- of the other tokens.
   | OutputStringLit !String
   -- ^ This represents a string literal.  For instance, @\"foobar\"@.
+  | OutputCharLit !String
+  -- ^ This represents a char literal.  For example, @'x'@ or @'\b'@
   | OutputNumberLit !String
   -- ^ This represents a numeric literal.  For example, @12345@ or @3.14159@.
   deriving (Data, Eq, Generic, Read, Show, Typeable)

src/Text/Pretty/Simple/Internal/OutputPrinter.hs

@@ -184,6 +184,18 @@ renderOutput (Output _ (OutputStringLit string)) = do
 
         readStr :: String -> String
         readStr s = fromMaybe s . readMaybe $ '"':s ++ "\""
+renderOutput (Output _ (OutputCharLit string)) = do
+  sequenceFold
+    [ useColorQuote
+    , pure "'"
+    , useColorReset
+    , useColorString
+    , pure (fromString string)
+    , useColorReset
+    , useColorQuote
+    , pure "'"
+    , useColorReset
+    ]
 
 -- | Replace non-printable characters with hex escape sequences.
 --