🚀 go-pugleaf

Hi,

  We have an assignment in this quarter about backward chaining. I try to 
use Turbo Prolog, but it seems has many troubles in it. 

/* Things that can be asked of the user are recorded as:
         askable(<goal>).

   Rules are recorded as:
         rule(<name>, <lhs-goal>, [<rhs-goal-1>, ..., <rhs-goal-n>]).

   Queries are written as:
         [<goal-1>, ..., <goal-n>] */


/* The empty query is always successful. */

backward([]).


/* A singleton query can be answered by the user if it is askable. */

backward([Goal]) :-
  askable(Goal),
  askUser(Goal).


/* A singleton query can be expanded if a rule is applicable. */

backward([Goal]) :-
  rule(_, Goal, Condition),
  backward(Condition).


/* A compound query can be solved recursively. */

backward([Goal | Goals]) :-
  \+(Goals = []),
  backward([Goal]),
  backward(Goals).



/* We assume that Goal is variable free.  This succeeds if the user says
   yes, explains and retries if the user says why,  and fails otherwise. */

askUser(Goal) :-
  write('Is this true: '),
  write(Goal),
  nl,
  read(X),
  (X = yes; (X = why, write('Unknown'), nl, askUser(Goal, Why))).



/* Now some sample program rules. */

rule(r1, isMammal(X), [hasHair(X), warmBlooded(X)]).

rule(r2, isBird(X), [hasFeathers(X), laysEggs(X)]).

rule(r4, isCat(X), [isMammal(X), purrs(X)]).

rule(r5, isRobin(X), [isBird(X), canFly(X)]).

rule(r5, isEmu(X), [isBird(X), cantFly(X)]).

askable(hasHair(_)).

askable(warmBlooded(_)).

askable(hasFeathers(_)).

askable(laysEggs(_)).

askable(purrs(_)).

askable(canFly(_)).

askable(cantFly(_)).

How can I transfer the clause like
  rule(r1, isMammal(X), [hasHair(X), warmBlooded(X)]).
into Turbo Prolog? It seems in Turbo Prolog does not have the form like
(..[..[..]..]) (not list).

Thank!!!
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