start work on cast expressions, add lots more test targets

Language/SQL/SimpleSQL/Pretty.lhs

@@ -47,6 +47,13 @@ back into SQL source text. It attempts to format the output nicely.
 >                     ,text "then" <+> scalarExpr t1]
 >     e el = text "else" <+> scalarExpr el
 > scalarExpr (Parens e) = parens $ scalarExpr e
+> scalarExpr (Cast e (TypeName tn)) =
+>     text "cast" <> parens (sep [scalarExpr e
+>                                ,text "as"
+>                                ,text tn])
+
+> scalarExpr (CastOp s (TypeName tn)) =
+>     text tn <+> quotes (text s)
 
 = query expressions
 

Language/SQL/SimpleSQL/Syntax.lhs

@@ -1,13 +1,14 @@
 
 > module Language.SQL.SimpleSQL.Syntax
->     (QueryExpr(..)
+>     (ScalarExpr(..)
+>     ,TypeName(..)
+>     ,QueryExpr(..)
 >     ,makeSelect
->     ,ScalarExpr(..)
+>     ,Duplicates(..)
+>     ,Direction(..)
 >     ,TableRef(..)
 >     ,JoinType(..)
 >     ,JoinCondition(..)
->     ,Duplicates(..)
->     ,Direction(..)
 >     ) where
 
 
@@ -23,8 +24,12 @@
 >                        [(ScalarExpr,ScalarExpr)] -- when branches
 >                        (Maybe ScalarExpr) -- else value
 >                 | Parens ScalarExpr
+>                 | Cast ScalarExpr TypeName
+>                 | CastOp String TypeName
 >                   deriving (Eq,Show)
 
+> data TypeName = TypeName String deriving (Eq,Show)
+
 > data QueryExpr
 >     = Select
 >       {qeDuplicates :: Duplicates