Data commit

Task/Hofstadter-Q-sequence/Tcl/hofstadter-q-sequence.tcl

@@ -0,0 +1,24 @@
+package require Tcl 8.5
+
+# Index 0 is not used, but putting it in makes the code a bit shorter
+set tcl::mathfunc::Qcache {Q:-> 1 1}
+proc tcl::mathfunc::Q {n} {
+    variable Qcache
+    if {$n >= [llength $Qcache]} {
+	lappend Qcache [expr {Q($n - Q($n-1)) + Q($n - Q($n-2))}]
+    }
+    return [lindex $Qcache $n]
+}
+
+# Demonstration code
+for {set i 1} {$i <= 10} {incr i} {
+    puts "Q($i) == [expr {Q($i)}]"
+}
+# This runs very close to recursion limit...
+puts "Q(1000) == [expr Q(1000)]"
+# This code is OK, because the calculations are done step by step
+set q [expr Q(1)]
+for {set i 2} {$i <= 100000} {incr i} {
+    incr count [expr {$q > [set q [expr {Q($i)}]]}]
+}
+puts "Q(i)<Q(i-1) for i \[2..100000\] is true $count times"