fix

Author: igr

java/src/main/java/v/o/i/d/monadsplain/Six.java

@@ -25,7 +25,7 @@ public IntegerWithHistory calculate(Function<Integer, IntegerWithHistory> operat
 			final IntegerWithHistory a = operation.apply(value);
 			return new IntegerWithHistory(
 					a.value,
-					join(history, join(history, a.history))
+					join(history, a.history)
 			);
 		}
 	}