Nodes of different colours represent the following:
Solid arrows point from a file to a file which it depends on. A file
is dependent upon another if the latter must be compiled before the former
can be.
program volatile_doctestuse vecfor_RPPtype(vector)::pt(0:2)pt(0)=3*expt(1)=1*expt(2)=2*exprint"(L1)",pt(0)%is_collinear(pt1=pt(1),pt2=pt(2))endprogram volatile_doctest