backtracking_ex_03.pi

%%% Entendendo BACKTRACKING
main => regra(10).
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
regra( 0 ) ?=>  printf("\n Chegou a 0 --- ZERO ") .

regra( X ) ?=>     %%% this rule is NOT backtrackable
         X > 7,
         println(xX_1 = X ),
         regra( X - 1 ).  

regra( X ) ?=>     %%% this rule is NOT backtrackable
         X == 7,
         println(xX_2 = X ),
         regra( X - 1 ).  

regra( X ) ?=>     %%% this rule is NOT backtrackable
         X < 7,
         X > 3,
         println(xX_3 = X ),
         regra( X - 1 ).  

regra( X ) =>     %%% this rule is NOT backtrackable
         X <= 3,
         println(xX_4 = X ),
         regra( X - 1 ).  
        	
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% 
/*

{Trace mode}
Picat> main race mode}
Picat> 
Picat> cl('backtracking_ex_03')
Compiling:: backtracking_ex_03.pi
backtracking_ex_03.pi compiled in 0 milliseconds
loading...

yes

{Trace mode}
Picat> main 
 +     spy
 -     nospy
 <     reset print depth to 10
 < i   set print depth to i
 a     abort
 h     help
<cr>   creep
 c     creep
 h     help
 ?     help
 l     leap
 n     nodebug
 r     repeat creep
 s     skip
 t     backtrace
 t i   backtrace from call #i
 u     undo, retrying the current call
 u i   undo, retrying call #i

   Call: (34) regra(2) ?c
   Call: (35) 2 > 7 ?a
{Trace mode}
Picat> 
*/