add support for named host parameters

Language/SQL/SimpleSQL/Parser.lhs

@@ -152,6 +152,16 @@ use in e.g. select * from t where a = ?
 > parameter :: Parser ValueExpr
 > parameter = Parameter <$ questionMark
 
+named parameter:
+
+select x from t where x > :param
+
+> hostParameter :: Parser ValueExpr
+> hostParameter =
+>     HostParameter
+>     <$> hostParameterToken
+>     <*> optionMaybe (keyword "indicator" *> hostParameterToken)
+
 == function application, aggregates and windows
 
 this represents anything which syntactically looks like regular C
@@ -572,6 +582,7 @@ fragile and could at least do with some heavy explanation.
 > term :: Parser ValueExpr
 > term = choice [literal
 >               ,parameter
+>               ,hostParameter
 >               ,caseValue
 >               ,cast
 >               ,try specialOpKs
@@ -887,6 +898,12 @@ make this choice.
 
 TODO: add "" inside quoted identifiers
 
+parses an identifier with a : prefix. The : isn't included in the
+return value
+
+> hostParameterToken :: Parser String
+> hostParameterToken = lexeme $ char ':' *> identifier
+
 todo: work out the symbol parsing better
 
 > symbol :: String -> Parser String

Language/SQL/SimpleSQL/Pretty.lhs

@@ -46,6 +46,11 @@ which have been changed to try to improve the layout of the output.
 > valueExpr (Iden i) = name i
 > valueExpr Star = text "*"
 > valueExpr Parameter = text "?"
+> valueExpr (HostParameter p i) =
+>     text (':':p)
+>     <+> maybe empty
+>         (\i' -> text "indicator" <+> text (':':i'))
+>         i
 
 > valueExpr (App f es) = name f <> parens (commaSep (map valueExpr es))
 

Language/SQL/SimpleSQL/Syntax.lhs

@@ -121,6 +121,11 @@
 >       -- means not in was used ('a not in (1,2)')
 >     | In Bool ValueExpr InPredValue
 >     | Parameter -- ^ Represents a ? in a parameterized query
+>     | HostParameter String (Maybe String) -- ^ represents a host
+>                                           -- parameter, e.g. :a. The
+>                                           -- Maybe String is for the
+>                                           -- indicator, e.g. :var
+>                                           -- indicator :nl
 >       deriving (Eq,Show,Read,Data,Typeable)
 
 > -- | Represents an identifier name, which can be quoted or unquoted.