June 2018 Update

Task/Hofstadter-Q-sequence/Julia/hofstadter-q-sequence-1.julia

@@ -1,9 +1,13 @@
-function Q(n)
-  N = maximum(n)
-  q = Array(Int, N)
-  q[1], q[2] = 1, 1
-  for i = 3:N
-    q[i] = q[i - q[i-1]] + q[i - q[i-2]]
-  end
-  return q[n]
+function hofstQseq(n, typerst::Type=Int)
+    nmax = maximum(n)
+    r = Vector{typerst}(nmax)
+    r[1] = 1
+    if nmax ≥ 2 r[2] = 1 end
+    for i in 3:nmax
+        r[i] = r[i - r[i - 1]] + r[i - r[i - 2]]
+    end
+    return r[n]
 end
+
+println("First ten elements of sequence: ", join(hofstQseq(1:10), ", "))
+println("1000-th element: ", hofstQseq(1000))

Task/Hofstadter-Q-sequence/Julia/hofstadter-q-sequence-2.julia

@@ -1,15 +1,3 @@
-julia> Q(1:10)
-10-element Array{Int64,1}:
- 1
- 1
- 2
- 3
- 3
- 4
- 5
- 5
- 6
- 6
-
-julia> Q(1000)
-502
+seq = hofstQseq(1:100_000)
+cnt = count(diff(seq) .< 0)
+println("$cnt elements are less than the preceding one.")

Task/Hofstadter-Q-sequence/Perl-6/hofstadter-q-sequence-1.pl6

@@ -6,3 +6,14 @@ class Hofstadter {
     return @!c[$i];
   }
 }
+
+# Testing:
+
+my Hofstadter $Q .= new();
+
+say "first ten: $Q[^10]";
+say "1000th: $Q[999]";
+
+my $count = 0;
+$count++ if $Q[$_ +1 ] < $Q[$_] for  ^99_999;
+say "In the first 100_000 terms, $count terms are less than their preceding terms";

Task/Hofstadter-Q-sequence/Perl-6/hofstadter-q-sequence-2.pl6

@@ -1,8 +1,12 @@
-my Hofstadter $Q .= new();
+my @Q = 1, 1, -> $a, $b {
+    (state $n = 1)++;
+    @Q[$n - $a] + @Q[$n - $b]
+} ... *;
 
-say "first ten: $Q[^10]";
-say "1000th: $Q[999]";
+# Testing:
 
-my $count = 0;
-$count++ if $Q[$_ +1 ] < $Q[$_] for  ^99_999;
-say "In the first 100_000 terms, $count terms are less than their preceding terms";
+say "first ten: ", @Q[^10];
+say "1000th: ", @Q[999];
+say "In the first 100_000 terms, ",
+   [+](@Q[1..100000] Z< @Q[0..99999]),
+   " terms are less than their preceding terms";