implementation: simplest case (insert element)

...so now the stage is set. We can reimplement
the handling of the list diff cases here in the context
of tree diff application. The additional twist of course
being the distinction between attribute and child scope

src/lib/diff/record-content-mutator.hpp

@@ -119,6 +119,12 @@ namespace diff{
           pos = attribs.begin();
         }
       
+      void
+      jumpToChildScope()
+        {
+          pos = children.begin();
+        }
+      
       void
       preAllocateStorage(size_t attribCnt, size_t childrenCnt)
         {

src/lib/diff/record.hpp

@@ -439,6 +439,14 @@ namespace diff{
           return *this;
         }
       
+      Mutator&
+      appendAttrib (VAL const& newAttrib)
+        {
+          REQUIRE (Rec::isAttribute(newAttrib));
+          record_.attribs_.push_back (newAttrib);
+          return *this;
+        }
+      
       Mutator&
       appendChild (VAL const& newChild)
         {

src/lib/diff/tree-diff-application.hpp

@@ -95,7 +95,14 @@ namespace diff{
       void
       ins (GenNode const& n)  override
         {
-          UNIMPLEMENTED("insert node");
+          if (n.isNamed())
+            target_.appendAttrib(n);
+          else
+            {
+              target_.appendChild(n);
+              if (content_.currIsAttrib())
+                content_.jumpToChildScope();
+            }
         }
       
       void

tests/library/diff/generic-record-update-test.cpp

@@ -147,6 +147,10 @@ namespace test{
           CHECK (rawElm == & *content.pos);
           ++content;
           CHECK ("b = β" == *content.pos);
+          content.jumpToChildScope();
+          CHECK ("γ" == *content.pos);
+          CHECK (!content.currIsAttrib());
+          CHECK (content.currIsChild());
           
           CHECK ( isnil (mut));
           CHECK (!isnil (content));