CVS difference for ais/ai-20302.txt

Differences between 1.17 and version 1.18
Log of other versions for file ais/ai-20302.txt

--- ais/ai-20302.txt	2005/02/26 00:51:54	1.17
+++ ais/ai-20302.txt	2005/04/13 05:37:28	1.18
@@ -662,7 +662,7 @@
 object V if:
  * it inserts or deletes elements of V, that is, it calls the Insert,
-   Insert_Space, Clear, Delete, Delete_Last, or Set_Length procedures with V
+   Insert_Space, Clear, Delete, or Set_Length procedures with V
    as a parameter; or
    AARM To Be Honest: Operations which are defined to be equivalent to
@@ -4785,41 +4785,14 @@
      Vector_Of_Lists.Swap (V, I, J);  -- vector operation
-For the definite form (the case here), this will make a copy of the
-element in order to perform the swap. However, we would prefer not to
-make a copy of this element, which is a list and hence potentially large
-(or otherwise expensive to copy). To avoid making a copy, we can use
-Move and nested processing routines:
-  procedure Swap
-    (V    : in out Vector_Of_Lists.Vector;
-     I, J : in     Extended_Index) is
-     procedure Process_I (IE : in out List) is
-        procedure Process_J (JE : in out List) is
-           IE_Temp : List;
-        begin
-           Move (Target => IE_Temp, Source => IE);
-           Move (Target => IE, Source => JE);
-           Move (Target => JE, Source => IE_Temp);
-        end;
-     begin
-        Update_Element (V, Index => J, Process => Process_J'Access);
-     end;
-  begin
-     Update_Element (V, Index => I, Process => Process_I'Access);
-  end Swap;
-To do the swap, we need direct visibility to both objects, so nested
-process procedures are required. We first move the list element at index I
-of the vector into a temporary. This allows another vector to by copied
-into that index position. We do that, moving the list element at index
-J into (empty) list element at index I. We then move the temporary
-(holding the list that was originally at index I) into the vector at
-index position J.
+This will (logically) make a copy of the element in order to perform the swap.
+Many implementations will avoid this copy; this is especially likely for
+the indefinite forms of these containers. But there is no guarantee that
+the copy can be avoided when using Swap.
+If we really must avoid making a copy (perhaps the element is potentially
+large), we need to use a list to store these elements. We then can use
+Swap_Links to swap the positions in the list without copying the elements.
 It's often the case that during an insertion you don't have an item

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