a (as far as R allows this) 'basic' block
CfgVertex.makeBlock() - for a helper function to create basic block vertices
something like an addition, ...
CfgVertex.makeExpression() - for a helper function to create expression vertices
something like an if, assignment, ... even though in the classical sense of R they are still expressions
CfgVertex.makeStatement() - for a helper function to create statement vertices
The type of a CfgVertex in the ControlFlowGraph.