report/src/planner.pl

   1 % -------------= Simple planner for situation calculus =---------------
   2 %
   3 % Executes an iterative deepening search, by default limited to a depth
   4 % of 15 levels
   5 %
   6 % plan.                 will search for a plan of maximum length
   7 % plan(M).      will search for a plan of maximum length up to M
   8 % plan(N,M).    will search for a plan of mimimum length N and maximum
   9 %               length M
  10 %
  11 %
  12 % Checklist for the definition of a domain and problem:
  13 %
  14 % - initial state                               initialize fluents in s0
  15 %
  16 % - possibility axioms                  poss( <action>(...), S ) :- <precond>
  17 %
  18 % - successor-state axioms              <fluent>( ..., result(A,S) ) :-
  19 %                                                                       <some events made it true>;     % or
  20 %                                                                       <it was true all along>,        % and
  21 %                                                                       not(<some events made it false>).
  22 %
  23 % - goal predicate                              goal(S) :- <goal conditions>
  24 %
  25
  26 % --------------------------= High Level =-----------------------------
  27
  28 % default number of iterations (15)
  29 plan :- plan(0, 15).
  30
  31 % given max number of iterations
  32 plan(MaxDepth) :- plan(0, MaxDepth).
  33
  34 % given min and max number of iterations
  35 plan(MinDepth, MaxDepth) :-
  36   M is MaxDepth+1, write('Trying plans of length: '),
  37   plan(Plan, MinDepth, M), nl, nl, writePlan(Plan).
  38
  39
  40
  41 % same as above, to be called from shell; include additional output
  42 % messages and halt to quit pl
  43 planner :- planner(0, 15).
  44 planner(MaxDepth) :- planner(0, MaxDepth).
  45 planner(MinDepth, MaxDepth) :-
  46   nl, plan(MinDepth, MaxDepth), nl, halt;
  47   write('\n\nNo plan has been found!'), nl, nl, halt.
  48
  49
  50
  51 % ---------------------------= Low Level =-----------------------------
  52
  53 % start from depth N, up to M
  54
  55 plan(P, N, M) :-
  56   N < M,
  57   debugoutput(write('\n\nPlans of length ')),
  58   writef('%w %f',[N]),
  59   seqplan(P, N, s0), !.
  60
  61 plan(P, N, M) :- N < M, O is N+1, plan(P, O, M).
  62
  63 seqplan( [], N, S ) :- N = 0, debugoutput(writeSituation(S)), goal(S).
  64 seqplan( [A|L], N, S) :- N > 0, M is N-1, result(A,S,S1), seqplan(L, M, S1).
  65
  66 result(E,S,result(E,S)) :- primitive_action(E), poss(E,S).
  67
  68 % -----------------------= Support Function =--------------------------
  69
  70 % debugoutput will be printed only if debug(on) is defined in the KB
  71 :- dynamic debug/1.
  72 :- multifile debug/1.
  73
  74 debug(on).
  75 debugoutput(A) :- debug(on), A, !; true.
  76
  77
  78 % prints a situation as a sequence of actions, starting from s0
  79 writeSituation(s0) :- write('\n s0').
  80 writeSituation(result(A,S)) :- writeSituation(S), writef(" > %w", [A]).
  81
  82 % prints a plan as a list of actions, numbered
  83
  84 writePlan(List) :-
  85   debugoutput(write('\nA plan has been found:\n\n')),
  86   writePlan(List,1).
  87
  88 writePlan([],_) :-
  89   nl.
  90
  91 writePlan([Action|List], Counter) :-
  92   writef('%3R %w\n',[Counter,Action]),
  93   Next is Counter+1,
  94   writePlan(List,Next).
  95
  96
  97 % hides some (unimportant) warnings from the pl interpreter
  98 :- style_check([-discontiguous, -singleton]).
  99
 100
 101
 102 % ---------------------------------------------------------------------
 103 % ---------------------------------------------------------------------