langs a-z

Task/Hofstadter-Q-sequence/PARI-GP/hofstadter-q-sequence.pari

@@ -0,0 +1,4 @@
+Q=vector(1000);Q[1]=Q[2]=1;for(n=3,#Q,Q[n]=Q[n-Q[n-1]]+Q[n-Q[n-2]]);
+Q1=vecextract(Q,"1..10");
+print("First 10 terms: "Q1,if(Q1==[1, 1, 2, 3, 3, 4, 5, 5, 6, 6]," (as expected)"," (in error)"));
+print("1000-th term: "Q[1000],if(Q[1000]==502," (as expected)"," (in error)"));

Task/Hofstadter-Q-sequence/PL-I/hofstadter-q-sequence-1.pli

@@ -0,0 +1,20 @@
+/* Hofstrader Q sequence for any "n". */
+
+H: procedure options (main);  /* 28 January 2012 */
+   declare n fixed binary(31);
+
+   put ('How many values do you want? :');
+   get (n);
+
+begin;
+   declare Q(n) fixed binary (31);
+   declare i fixed binary (31);
+
+   Q(1), Q(2) = 1;
+   do i = 1 upthru n;
+      if i >= 3 then Q(i) = ( Q(i - Q(i-1)) + Q(i - Q(i-2)) );
+      if i <= 20 then put skip list ('n=' || trim(i), Q(i));
+   end;
+   put skip list ('n=' || trim(i), Q(i));
+end;
+end H;

Task/Hofstadter-Q-sequence/PL-I/hofstadter-q-sequence-2.pli

@@ -0,0 +1,6 @@
+   declare tally fixed binary (31) initial (0);
+
+   do i = 1 to n-1;
+      if Q(i) > Q(i+1) then tally = tally + 1;
+   end;
+   put skip data (tally);

Task/Hofstadter-Q-sequence/Pascal/hofstadter-q-sequence.pascal

@@ -0,0 +1,24 @@
+Program HofstadterQSequence (output);
+
+const
+  limit = 100000;
+
+var
+  q: array [1..limit] of longint;
+  i, flips: longint;
+
+begin
+  q[1] := 1;
+  q[2] := 1;
+  for i := 3 to limit do
+    q[i] := q[i - q[i - 1]] + q[i - q[i - 2]];
+  for i := 1 to 10 do
+    write(q[i], ' ');
+  writeln;
+  writeln(q[1000]);
+  flips := 0;
+  for i := 1 to limit - 1 do
+    if q[i] > q[i+1] then
+      inc(flips);
+  writeln('Flips: ', flips);
+end.

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

@@ -0,0 +1,14 @@
+class Hofstadter {
+  has @!c = 1,1;
+  multi method postcircumfix:<[ ]> ($me: Int $i) {
+    @!c.push($me[@!c.elems-$me[@!c.elems-1]] +
+	     $me[@!c.elems-$me[@!c.elems-2]]) until @!c.exists($i);
+    return @!c[$i];
+  }
+
+  # note that this method isn't strictly required for solving the task,
+  # it's just a wrapper to get more than one item
+  multi method postcircumfix:<[ ]> ($me: Range $is) {
+    return gather {take $me[$_] for $is.iterator;}
+  }
+}

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

@@ -0,0 +1,8 @@
+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-3.pl6

@@ -0,0 +1,4 @@
+constant @Q = 1, 1, -> $a, $b {
+    (state $n = 1)++;
+    @Q[$n - $a] + @Q[$n - $b]
+} ... *;

Task/Hofstadter-Q-sequence/Perl-6/hofstadter-q-sequence-4.pl6

@@ -0,0 +1,5 @@
+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";

Task/Hofstadter-Q-sequence/Seed7/hofstadter-q-sequence.seed7

@@ -0,0 +1,38 @@
+$ include "seed7_05.s7i";
+
+const type: intHash is hash [integer] integer;
+
+var intHash: qHash is intHash.value;
+
+const func integer: q (in integer: n) is func
+  result
+    var integer: q is 1;
+  begin
+    if n in qHash then
+      q := qHash[n];
+    else
+      if n > 2 then
+        q := q(n - q(pred(n))) + q(n - q(n - 2));
+      end if;
+      qHash @:= [n] q;
+    end if;
+  end func;
+
+const proc: main is func
+  local
+    var integer: n is 0;
+    var integer: less_than_preceding is 0;
+  begin
+    writeln("q(n) for n = 1 .. 10:");
+    for n range 1 to 10 do
+      write(q(n) <& " ");
+    end for;
+    writeln;
+    writeln("q(1000)=" <& q(1000));
+    for n range 2 to 100000 do
+      if q(n) < q(pred(n)) then
+        incr(less_than_preceding);
+      end if;
+    end for;
+    writeln("q(n) < q(n-1) for n = 2 .. 100000: " <& less_than_preceding);
+  end func;

Task/Hofstadter-Q-sequence/XPL0/hofstadter-q-sequence.xpl0

@@ -0,0 +1,13 @@
+code ChOut=8, CrLf=9, IntOut=11;
+int  N, C, Q(100_001);
+[Q(1):= 1;  Q(2):= 1;  C:= 0;
+for N:= 3 to 100_000 do
+        [Q(N):= Q(N-Q(N-1)) + Q(N-Q(N-2));
+        if Q(N) < Q(N-1) then C:= C+1;
+        ];
+for N:= 1 to 10 do
+        [IntOut(0, Q(N));  ChOut(0, ^ )];
+CrLf(0);
+IntOut(0, Q(1000));  CrLf(0);
+IntOut(0, C);  CrLf(0);
+]