anchor.diff:  
   %% Returns a zero-arity function returning the individual who won a single
   %% roulette run. Multiple runs may return the same individual.
  -roulette_wheel_fn(Plist, _) ->
  +roulette_selection_fn(Plist, _) ->
       {plist, Slotted, total, N} = assign_slots(Plist),
       fun () ->
               Val = random:uniform()*N,
  
positive.code:             I
      end.
  
  roulette_wheel(Plist, _) ->
      {plist, Slotted, total, N} = assign_slots(Plist),
      Val = random:uniform()*N,
      {indiv, I,
  
negative.code:                      F1 =< F2.
  
  %% Do not do any scaling of the fitnesses.
  fitness_scale(Plist, _) ->
      Plist.
  
  sigma_scale(Plist, _) ->
  