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  1. %% Producer provides {peek, pull} interface to a generator
  2.  
  3. peek( prod(Curr,Next), Curr, prod(Curr,Next)).
  4. peek( prod(Next),         C, prod(C,N)  ):- next(Next,C,N).
  5. pull( prod(Curr,Next), Curr, prod(Next) ).
  6. pull( prod(Next),         C, prod(N)    ):- next(Next,C,N).
  7.  
  8. %% collect N elements produced by producer in a row
  9.  
  10. take( 0, Prod, Z-Z, Prod).
  11. take( N, Prod, [A|B]-Z, PZ):- N>0, !, 
  12.   pull(Prod, A, P1), N1 is N-1,
  13.   take(N1,P1,B-Z,PZ).
  14.  
  15. %% Generator provides specific {next} implementation
  16.  
  17. next( hamm( A2,B,C3,D,E5,F,[H|G] ), H, hamm(X,U,Y,V,Z,W,G) ):- 
  18.   H is min(A2, min(C3,E5)),
  19.   (   A2 =:= H -> B=[N2|U],X is N2*2 ; (X,U)=(A2,B) ),
  20.   (   C3 =:= H -> D=[N3|V],Y is N3*3 ; (Y,V)=(C3,D) ),
  21.   (   E5 =:= H -> F=[N5|W],Z is N5*5 ; (Z,W)=(E5,F) ).
  22.  
  23. mkHamm( prod( hamm(1,X,1,X,1,X,X)) ).            % int_overflow @ 20,000 already
  24.  
  25. main(N) :- 
  26.   statistics(inferences,I1),
  27.   ( mkHamm(P),take(20,P,A-[],_),write(A),nl, 
  28.     take(1691-1,P,_,P2),take(2,P2,B-[],_),    write(B), nl,  
  29.     take(  N  -1,P,_,P3),take(2,P3,[C1|_]-_,_),   write(C1), nl 
  30.   ),
  31.   statistics(inferences,I2),
  32.   Infs is I2 - I1, nl, write('   '), write(Infs), write(' Infs').
  33.  
  34. /*
  35. ON INTS:
  36.  
  37. [1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24, 25, 27, 30, 32, 36]
  38. [2125764000, 2147483648]
  39. 288325195312500000
  40.  
  41. 10k:   288325195312500000    70273 Infs    time:  0.06s    memory:  6204 kB
  42.  
  43. ON FLOATS (w/ overwhelming precision errors):
  44.  
  45. 10,000     2.56494e+17       70273 Infs    time:  0.06s    memory:  6204 kB
  46. 100k:      5.14728e+24      610273 Infs    time:  0.54s    memory:  6204 kB
  47. 500k:      1.02580e+28     3010273 Infs    time:  4.60s    memory:  6204 kB     
  48. 1mln:      2.46193e+29     6010273 Infs    time: 13.64s    memory:  6204 kB 
  49. */
Success #stdin #stdout 0.06s 6204KB
comments (?)
stdin 
main(10000).
stdout 
[1, 2, 3, 4, 5, 6, 8, 9, 10, 12, 15, 16, 18, 20, 24, 25, 27, 30, 32, 36]
[2125764000, 2147483648]
288325195312500000

   70291 Infs
https://ideone.com/tv5Cy
language:
Prolog (swi 7.6.4)
created:
14 years ago
visibility:
secret

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