Re: Help- error in executing "retract" predicate

[Vic Bancroft]

You may also want to use the initialization/1 predicate to set up your 
dynamic predicates.  For example, given a file, vidhya.pl, containing,

  :- dynamic( sam/1 ).
  
  :- initialization( assertz( sam( 1 ) ) ).
  
  soln :-
    sam(X),
    retract(sam(X)),
    write(success).
  
when consulted, in the following behavior,

  | ?- [vidhya].
  compiling /home/bancroft/src/prolog/vidhya.pl for byte code...
  /home/bancroft/src/prolog/vidhya.pl compiled, 9 lines read - 583 bytes 
written, 63 ms
  
  (10 ms) yes
  | ?- listing.
  
  sam(1).
  
  soln :-
        sam(A),
        retract(sam(A)),
        write(success).
  
  yes
  | ?- soln.
  success
  
  yes
  | ?- listing.
  
  
  soln :-
        sam(A),
        retract(sam(A)),
        write(success).
  
  yes
  
more,
l8r,
v

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