2007 01 11

Tail Calls Tail calls were recenlty readded as a feature to Io. Here is a small example that compares their performance with normal recursive calls: count := 10000 r := 100 b := method(x, if(x > r, return x); b(x + 1)) t1 := Date secondsToRun(count repeat(b(1))) writeln((count*r/t1) round, " recursive calls per second") b := method(x, if(x > r, return x); tailCall(x + 1)) t2 := Date secondsToRun(count repeat(b(1))) writeln((count*r/t2) round, " tail calls per second") writeln("tail calls are ", (t1/t2) round, " times faster") And the results on a 2Ghz Mac Book Pro: 456328 recursive calls per second 1369613 tail calls per second tail calls are 3 times faster Not a huge speed difference for this simple example but for deep recursion, it can save a lot of stack space.