[r2005-06-02 11:52:35 by afrisch] Field access for XML attibutes

Original author: afrisch
Date: 2005-06-02 11:52:35+00:00

CHANGES

-0.3.2+2
+Since 0.3.2
    * Added split_atom, make_atom. Removed atom_of.
-
-0.3.2+1
    * Added char_of_int built_in function.
-   * Now int_of also accepts octal binary and hexadecimals
-
+   * Now int_of also accepts octal binary and hexadecimals.
+   * The field access also works for XML element attributes.
 
 0.3.2
    * Bug fix in configure

runtime/eval.ml

@@ -302,7 +302,9 @@ and eval_xtrans_aux env brs acc = function
   | _ -> acc
 
 and eval_dot l = function
-  | Value.Record r -> LabelMap.assoc l r
+  | Value.Record r 
+  | Value.Xml (_,Value.Record r,_)
+  | Value.XmlNs (_,Value.Record r,_,_) -> LabelMap.assoc l r
   | v -> 
       Value.print Format.std_formatter v;
       failwith ("Cannot find field " ^ (Label.to_string (LabelPool.value l)))

typing/typer.ml

@@ -874,12 +874,20 @@ and type_check' loc env e constr precise = match e with
       type_check_string loc env 0 s i j e constr precise
 
   | Dot (e,l) ->
-      let t = type_check env e Types.Record.any true in
-      let t = 
-        try Types.Record.project t l
-        with Not_found -> raise_loc loc (WrongLabel(t,l))
-      in
-      verify loc t constr
+      let expect_rec = Types.record l (Types.cons constr) in
+      let expect_elt = 
+	Types.xml 
+	  Types.any_node 
+	  (Types.cons (Types.times (Types.cons expect_rec) Types.any_node)) in
+      let t = type_check env e (Types.cup expect_rec expect_elt) precise in
+      let t_elt =
+	let t = Types.Product.pi2 (Types.Product.get ~kind:`XML t) in
+	let t = Types.Product.pi1 (Types.Product.get t) in
+	t in
+      if not precise then constr
+      else
+	(try Types.Record.project (Types.cup t t_elt) l
+	 with Not_found -> assert false)
 
   | RemoveField (e,l) ->
       let t = type_check env e Types.Record.any true in

web/manual/expressions.xml

@@ -550,6 +550,27 @@ evaluates to
 ]]></code>.
 </p>
 
+<p>
+There is another form of projection to extract attributes:
+</p>
+<sample><![CDATA[
+%%e%%/@%%l%%
+]]></sample>
+<p>
+which is equivalent to:
+</p>
+<sample><![CDATA[
+transform %%e%% with <_ l=l>_ -> l
+]]></sample>
+<p>
+The dot notation can also be used to extract the value of the
+attribute for one XML element:
+</p>
+<sample><![CDATA[
+# <a x=3>[].x;;
+- : 3 = 3
+]]></sample>
+
 </section>
 
 <section title="Iteration over XML trees">