VARKON Version 1.15 1997-10-16

### Group

A group is a non geometric entity with a name and a list of members. In its simplest form a group can be used to associate a text with a single entity.....
arc_1pos(#1,vec(0,0),10);
group(#2,"screwhole",#1);
In this example a group is created with name = screwhole and the arc #1 is its only member. The significance of this would be that the arc represents a screw hole, information that could be used for example by another application during process planning or cost estimation. The group entity is implemented using two way pointers between the group and its members. The arc entity knows which group it belongs to and the group entity knows where its members are.
A group can also be used to combine several entities into a common structure...
poi_free(#1,vec(0,0));
poi_free(#2,vec(100,0));
poi_free(#3,vec(50,50));
group(#4,"triangle",#1,#2,#3);
In this case a group #4 is created with three points as members and name = triangle. Each point holds information that it belongs to group #4 and the group itself holds its name and the identity of its three members. Any entity including group itself can belong to a maximum of 3 different groups at the same time.
The group entity is a way to create a structural relationship or context in much the same way as the part. A part is more powerful but also more complex to use. A part needs a defining MODULE, uses parameters and holds any number of entities while a group only has a name and can only hold a maximum of 100 members.
In many cases it turns out best to use the part to describe different objects and the group to describe smaller structures within the object. A group can also be used to express a relation between two different parts.

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