add positional arg to the syntax and parser

Language/SQL/SimpleSQL/Parse.lhs

@@ -586,6 +586,11 @@ select x from t where x > :param
 >      <$> hostParamTok
 >      <*> optionMaybe (keyword "indicator" *> hostParamTok)]
 
+== positional arg
+
+> positionalArg :: Parser ValueExpr
+> positionalArg = PositionalArg <$> positionalArgTok
+
 == parens
 
 value expression parens, row ctor and scalar subquery
@@ -1238,6 +1243,7 @@ documenting/fixing.
 > term :: Parser ValueExpr
 > term = choice [simpleLiteral
 >               ,parameter
+>               ,positionalArg
 >               ,star
 >               ,parensExpr
 >               ,caseExpr
@@ -2048,6 +2054,13 @@ It is only allowed when all the strings are quoted with ' atm.
 >       L.PrefixedVariable c p -> Just (c:p)
 >       _ -> Nothing)
 
+> positionalArgTok :: Parser Int
+> positionalArgTok = mytoken (\tok ->
+>     case tok of
+>       L.PositionalArg p -> Just p
+>       _ -> Nothing)
+
+
 > sqlNumberTok :: Bool -> Parser String
 > sqlNumberTok intOnly = mytoken (\tok ->
 >     case tok of

Language/SQL/SimpleSQL/Pretty.lhs

@@ -52,6 +52,7 @@ which have been changed to try to improve the layout of the output.
 > valueExpr _ (Iden i) = names i
 > valueExpr _ Star = text "*"
 > valueExpr _ Parameter = text "?"
+> valueExpr _ (PositionalArg n) = text $ "$" ++ show n
 > valueExpr _ (HostParameter p i) =
 >     text p
 >     <+> me (\i' -> text "indicator" <+> text i') i

Language/SQL/SimpleSQL/Syntax.lhs

@@ -109,6 +109,7 @@
 >     | Star
 
 >     | Parameter -- ^ Represents a ? in a parameterized query
+>     | PositionalArg Int -- ^ Represents an e.g. $1 in a parameterized query
 >     | HostParameter String (Maybe String) -- ^ represents a host
 >                                           -- parameter, e.g. :a. The
 >                                           -- Maybe String is for the

tools/Language/SQL/SimpleSQL/ValueExprs.lhs

@@ -60,9 +60,9 @@ Tests for parsing value expressions
 >     ]
 
 > parameter :: TestItem
-> parameter = Group "parameter" $ map (uncurry (TestValueExpr ansi2011))
+> parameter = Group "parameter"
->     [("?", Parameter)
+>     [TestValueExpr ansi2011 "?" Parameter
->     ]
+>     ,TestValueExpr postgres "$13" $ PositionalArg 13]
 
 
 > dots :: TestItem