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 stringifor_string_ttype(string)::astringlogical::test_passed(1)astring='+++ab-++cre-++cre-ab+++++'test_passed(1)=astring%unique(substring='+')//''=='+ab-+cre-+cre-ab+'print'(L1)',all(test_passed)endprogram volatile_doctest