add support for '' in string literals

Language/SQL/SimpleSQL/Parser.lhs

@@ -724,7 +724,13 @@ String literals: limited at the moment, no escaping \' or other
 variations.
 
 > stringLiteral :: P String
-> stringLiteral = char '\'' *> manyTill anyChar (symbol_ "'")
+> stringLiteral = (char '\'' *> manyTill anyChar (char '\'')
+>                  >>= optionSuffix moreString) <* whiteSpace
+>   where
+>     moreString s0 = try $ do
+>         void $ char '\''
+>         s <- manyTill anyChar (char '\'')
+>         optionSuffix moreString (s0 ++ "'" ++ s)
 
 number literals
 

Language/SQL/SimpleSQL/Pretty.lhs

@@ -28,7 +28,11 @@
 = scalar expressions
 
 > scalarExpr :: ScalarExpr -> Doc
-> scalarExpr (StringLit s) = quotes $ text s
+> scalarExpr (StringLit s) = quotes $ text $ doubleUpQuotes s
+>   where doubleUpQuotes [] = []
+>         doubleUpQuotes ('\'':cs) = '\'':'\'':doubleUpQuotes cs
+>         doubleUpQuotes (c:cs) = c:doubleUpQuotes cs
+
 > scalarExpr (NumLit s) = text s
 > scalarExpr (IntervalLit v u p) =
 >     text "interval" <+> quotes (text v)