@@ -1,24 +1,22 @@
 import util;
 import game;
 import driver;
-import std.c.stdlib;
 import core.stdc.signal;
 
 class NilOutput : GameObserver
 {
 	this(const(Game) g) {}
-	override bool on_game_changed(char c, const(Game) g, bool finished) {return false;}
+	override void on_game_changed(char c, const(Game) g, bool finished) {}
 }
 
 class StdOutput : GameObserver
 {
 	this(const(Game) g) {}
-	override bool on_game_changed(char c, const(Game) g, bool finished)
+	override void on_game_changed(char c, const(Game) g, bool finished)
 	{
 		stdout.write(c);
 		stdout.flush();
-		return false;
 	}
 }
 
 class GuardedOutput : GameObserver
@@ -28,16 +26,15 @@
 		setup_sigint_handling();
 		ideal_log ~= g.score_if_abort_now;
 	}
 
-	override bool on_game_changed(char c, const(Game) g, bool finished)
+	override void on_game_changed(char c, const(Game) g, bool finished)
 	{
 		log ~= c;
 		score_log ~= g.score;
 		ideal_log ~= g.score_if_abort_now;
 		if(finished)
 			flush();
-		return false;
 	}
 
 private:
 	string log;