X-Git-Url: http://gitweb.michael.orlitzky.com/?a=blobdiff_plain;f=src%2FXml.hs;h=ec409ac1b8f2eda9abda3312b020a347584c6cd0;hb=746bca130defe04f4f74b22149a9a300bfd3af65;hp=780a64e6473815ecd0ec88d4257e4d1ce231373c;hpb=4595387816651b26e4c163e5c416c5caa01d17cf;p=dead%2Fhtsn-import.git

diff --git a/src/Xml.hs b/src/Xml.hs
index 780a64e..ec409ac 100644
--- a/src/Xml.hs
+++ b/src/Xml.hs
@@ -4,6 +4,7 @@
 -- | General XML stuff.
 --
 module Xml (
+  Child(..),
   DtdName(..),
   FromXml(..),
   FromXmlFk(..),
@@ -11,6 +12,7 @@ module Xml (
   parse_opts,
   pickle_unpickle,
   unpickleable,
+  unsafe_read_document,
   unsafe_unpickle )
 where
 
@@ -22,6 +24,7 @@ import Text.XML.HXT.Core (
   (/>),
   PU,
   SysConfigList,
+  XmlTree,
   isElem,
   no,
   readDocument,
@@ -34,6 +37,8 @@ import Text.XML.HXT.Core (
   xunpickleVal,
   yes )
 
+
+
 -- | Common associated type shared by 'FromXml' and 'FromXmlFk'. This
 --   basically just forces the client to define the \"database
 --   version\" of his type.
@@ -58,22 +63,30 @@ class (ToDb a) => FromXml a where
   from_xml :: a -> Db a
 
 
--- | Some database types cannot be constructed from the XML type
---   alone; they must be supplied a foreign key to a parent object
---   first. Members of this class can be converted from an XML
---   representation to a database representation in this manner.
+-- | A class for XML representations which are children of other
+--   elements. The foal is to associate a child XML element with its
+--   parent element's database type. This is required to construct the
+--   database analogue of @a@ in 'FromXmlFk'.
 --
-class (ToDb a) => FromXmlFk a where
+class Child a where
   -- | The type of our parent object, i.e. to the type to whom our
   --   foreign key will point.
   type Parent a :: *
 
+
+-- | Some database types cannot be constructed from the XML type
+--   alone; they must be supplied a foreign key to a parent object
+--   first. Members of this class can be converted from an XML
+--   representation to a database representation in this manner.
+--
+class (Child a, ToDb a) => FromXmlFk a where
   -- | The function that produces a @Db a@ out of a foreign key and an
   --   @a@. The parameter order makes it easier to map this function
   --   over a bunch of things.
   from_xml_fk :: DefaultKey (Parent a) -> a -> Db a
 
 
+
 -- | Represents the DTD filename (\"SYSTEM\") part of the DOCTYPE
 --   definition.
 newtype DtdName = DtdName String
@@ -153,3 +166,11 @@ unpickleable filepath unpickler = do
 unsafe_unpickle :: FilePath -> PU a -> IO a
 unsafe_unpickle filepath unpickler =
   fmap head $ runX $ xunpickleDocument unpickler parse_opts filepath
+
+
+-- | Read an XML document from a 'FilePath' into an XmlTree. Explode if it
+--   doesn't work.
+--
+unsafe_read_document :: FilePath -> IO XmlTree
+unsafe_read_document filepath =
+  fmap head $ runX $ readDocument parse_opts filepath