Functional programming pays off (part 2)

We continue to gain from our use of functional programming techniques.

Using just the "immutable object" technique, we've improved our code and made our programming lives easier. Immutable objects have given us two benefits this week.

The first benefit: less code. We revised our test framework to use immutable objects. Rather than instantiating a test object (which exercises the true object under test) and asking it to run the tests, we now instantiate the test object and it runs the tests immediately. We then simply ask it for the results. Our new code is simpler than before, and contains fewer lines of code.

The second benefit: we can extract classes from one program and add them to another -- and do it easily. This is a big win. Often (too often), extracting a class from one program is difficult, because of dependencies and side effects. The one class requires other classes, not just direct dependencies but classes "to the side" and "above" in order to function. In the end, one must import most of the original system!

With immutable objects, we have eliminated side effects. Our code has no "side" or "above" dependencies, and has fewer direct dependencies. Thus, it is much easier for us to move a class from one program into another.

We took advantage of both of these effects this week, re-organizing our code. We were productive because our code used immutable objects.