-- File:	Compare.cdl
-- Created:	Wed Sep 23 10:52:07 1992
-- Author:	Christian CAILLET
--		<cky@phobox>
---Copyright:	 Matra Datavision 1992


class Compare  from IFGraph  inherits GraphContent

    	---Purpose : this class evaluates effect of two compared sub-parts :
    	--           cumulation (union), common part (intersection-overlapping)
    	--           part specific to first sub-part or to the second one
    	--           Results are kept in a Graph, several question can be set
    	--           Basic Iteration gives Cumulation (union)

uses Transient, EntityIterator, Graph

is

    Create (agraph : Graph) returns Compare;
    ---Purpose : creates empty Compare, ready to work

    GetFromEntity (me : in out; ent : any Transient; first : Boolean);
    ---Purpose : adds an entity and its shared ones to the list :
    --           first True means adds to the first sub-list, else to the 2nd

    GetFromIter (me : in out; iter : EntityIterator; first : Boolean);
    ---Purpose : adds a list of entities (as an iterator) as such, that is,
    --           their shared entities are not considered (use AllShared to
    --           have them)
    --           first True means adds to the first sub-list, else to the 2nd

    Merge (me : in out);
    ---Purpose : merges the second list into the first one, hence the second
    --           list is empty

    RemoveSecond (me : in out);
    ---Purpose : Removes the contents of second list

    KeepCommon (me : in out);
    ---Purpose : Keeps only Common part, sets it as First list and clears
    --           second list

    ResetData (me : in out);
    ---Purpose : Allows to restart on a new data set

    	-- --   Results   -- --
    	--   More-Next-Value-Entity give all entities taken into the Cumulation
    	--   other informations are provided, as EntityIterator : hence they
    	--   are available for other evaluations

    Evaluate (me : in out) is redefined;
    ---Purpose : Recomputes result of comparing to sub-parts

    Common (me) returns EntityIterator;
    ---Purpose : returns entities common to the both parts

    FirstOnly (me) returns EntityIterator;
    ---Purpose : returns entities which are exclusively in the first list

    SecondOnly (me) returns EntityIterator;
    ---Purpose : returns entities which are exclusively in the second part

fields

    thegraph : Graph;

end Compare;