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Task/Van-der-Corput-sequence/Prolog/van-der-corput-sequence.pro

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+% vdc( N, Base, Out )
+% Out = the Van der Corput representation of N in given Base
+vdc( 0, _, [] ).
+vdc( N, Base, Out ) :-
+    Nr is mod(N, Base),
+    Nq is N // Base,
+    vdc( Nq, Base, Tmp ),
+    Out = [Nr|Tmp].
+
+% Writes every element of a list to stdout; no newlines
+write_list( [] ).
+write_list( [H|T] ) :-
+    write( H ),
+    write_list( T ).
+
+% Writes the Nth Van der Corput item.
+print_vdc( N, Base ) :-
+    vdc( N, Base, Lst ),
+    write('0.'),
+    write_list( Lst ).
+print_vdc( N ) :-
+    print_vdc( N, 2 ).
+
+% Prints the first N+1 elements of the Van der Corput
+% sequence, each to its own line
+print_some( 0, _ ) :-
+    write( '0.0' ).
+print_some( N, Base ) :-
+    M is N - 1,
+    print_some( M, Base ),
+    nl,
+    print_vdc( N, Base ).
+print_some( N ) :-
+    print_some( N, 2 ).
+
+test :-
+   writeln('First 10 members in base 2:'),
+   print_some( 9 ),
+   nl,
+   write('7th member in base 4 (stretch goal) => '),
+   print_vdc( 7, 4 ).