Resolving dependencies...
cabal: Could not resolve dependencies:
trying: prolog-graph-0.1.0.2 (user goal)
trying: containers-0.5.7.1/installed-0.5... (dependency of
graphviz-2999.18.1.2)
next goal: prolog (dependency of prolog-graph-0.1.0.2)
rejecting: prolog-0.2.0.1 (conflict: prolog-graph => prolog==0.1.*)
rejecting: prolog-0.1 (conflict: containers==0.5.7.1/installed-0.5..., prolog
=> containers>=0.4 && <0.5)
Backjump limit reached (currently 2000, change with --max-backjumps or try to
run with --reorder-goals).