# 8.20.3.6 IfcEdgeLoop

## 8.20.3.6.1 Semantic definition

Informal Propositions:

1. The genus of the IfcEdgeLoop shall be 1 or greater.
2. The Euler formula shall be satisfied: (number of vertices) + genus - (number of edges) = 1;
3. No edge may be referenced more than once by the same IfcEdgeLoop with the same sense. For this purpose, an edge which is not an oriented edge is considered to be referenced with the sense TRUE.

## 8.20.3.6.5 Formal representation

ENTITY IfcEdgeLoop
SUBTYPE OF (IfcLoop);
EdgeList : LIST [1:?] OF IfcOrientedEdge;
DERIVE
Ne : IfcInteger := SIZEOF(EdgeList);
WHERE
IsClosed : (EdgeList[1].EdgeStart) :=: (EdgeList[Ne].EdgeEnd);
END_ENTITY;