Prolog solutions for challenge 098.

3 files changed, 76 insertions, 0 deletions

diff --git a/challenge-098/adam-russell/blog1.txt b/challenge-098/adam-russell/blog1.txt
new file mode 100644
index 0000000000..816788ff86
--- /dev/null
+++ b/challenge-098/adam-russell/blog1.txt
@@ -0,0 +1 @@
+http://www.rabbitfarm.com/cgi-bin/blosxom/prolog/2021/02/07 
diff --git a/challenge-098/adam-russell/prolog/ch-1.p b/challenge-098/adam-russell/prolog/ch-1.p
new file mode 100644
index 0000000000..7a6757830a
--- /dev/null
+++ b/challenge-098/adam-russell/prolog/ch-1.p
@@ -0,0 +1,37 @@
+:-dynamic(position/1).
+:-initialization(main).
+
+position(0).
+
+read_n_chars(Stream, N, Chars):-
+    read_n_chars(Stream, N, [], Chars).
+read_n_chars(_, 0, ByteAccum, Chars):-
+    atom_codes(Chars, ByteAccum).    
+read_n_chars(Stream, N, ByteAccum, Chars):-
+    \+ at_end_of_stream(Stream),
+    get_byte(Stream, C),
+    N0 is N - 1,
+    append(ByteAccum, [C], ByteAccum0),
+    read_n_chars(Stream, N0, ByteAccum0, Chars).
+read_n_chars(Stream, _, ByteAccum, Chars):-
+    at_end_of_stream(Stream),
+    read_n_chars(Stream, 0, ByteAccum, Chars).
+    
+read_n(File, N, Chars):-
+    open(File, read, Stream,[type(binary),reposition(true)]),
+    position(Position),
+    seek(Stream, bof, Position, _),
+    read_n_chars(Stream, N, Chars),
+    X is N + Position,
+    retract(position(Position)),
+    asserta(position(X)),
+    close(Stream).
+    
+main:-
+    read_n('../ch-1.dat', 4, Chars0),
+    write(Chars0), nl,
+    read_n('../ch-1.dat', 4, Chars1),
+    write(Chars1), nl,
+    read_n('../ch-1.dat', 4, Chars2),
+    write(Chars2), nl,
+    halt.
\ No newline at end of file
diff --git a/challenge-098/adam-russell/prolog/ch-2.p b/challenge-098/adam-russell/prolog/ch-2.p
new file mode 100644
index 0000000000..c31d54817f
--- /dev/null
+++ b/challenge-098/adam-russell/prolog/ch-2.p
@@ -0,0 +1,38 @@
+:-initialization(main).
+
+needle_haystack([H|T], N, Index):-
+    ((N < H, Index is 0); 
+       (last(T, Last), N > Last, 
+       length([H|T], Length), Index is Length)).
+needle_haystack([H|T], N, Index):-
+    needle_haystack([H|T], N, 0, Index).
+needle_haystack([], _, Index, Index).    
+needle_haystack([_|[]], _, Index, Index).
+needle_haystack([H0, _|_], N, Counter, Index):-
+    H0 == N,
+    Index is Counter.
+needle_haystack([_, H1|_], N, Counter, Index):-
+    H1 == N,
+    Index is Counter + 1.
+needle_haystack([H0, H1|T], N, Counter, Index):-
+    H0 \== N,
+    H1 \== N,
+    \+ between(H0, H1, N),
+    C is Counter + 2,
+    needle_haystack(T, N, C, Index).
+needle_haystack([H0, H1|_], N, Counter, Index):-
+    H0 \== N,
+    H1 \== N,
+    between(H0, H1, N),
+    Index is Counter + 1.
+            
+main:-
+    needle_haystack([1, 2, 3, 4], 3, Index0),
+    write(Index0), nl,
+    needle_haystack([1, 3, 5, 7], 6, Index1),
+    write(Index1), nl,
+    needle_haystack([12, 14, 16, 18], 10, Index2),
+    write(Index2), nl,
+    needle_haystack([11, 13, 15, 17], 19, Index3),
+    write(Index3), nl,
+    halt.
\ No newline at end of file