Summary
For many years we've been using statically typed languages for the safety they offer. But now, as we all gradually adopt Test Driven Development, are we going to find that safety redundant? Will we therefore decide that the flexibility of dynamically typed languages is desirable?

I've been a statically typed bigot for quite a few years. I learned my lesson the hard way while using C. Too many systems crashed in the field due to silly typing errors. When C++ came out, I was an avid adopter, and rabid enforcer of strong typing. I scoffed at the smalltalkers who whined about the loss of flexibility. Safety, after all, was far more important than flexibility -- and besides, we can keep our software flexible AND statically typed, if we just follow good dependency management principles.

Four years ago I got involved with Extreme Programming. I liked the pragmatic emphasis it placed upon developing software. I also liked the emphasis it put on testing. Since then I have become test infected. I can no longer concieve of writing software without using test driven development. I can't imagine not having a comprehensive suite of unit tests to back up my development.

About two years ago I noticed something. I was depending less and less on the type system for safety. My unit tests were preventing me from making type errors. The more I depended upon the unit tests, the less I depended upon the type safety of Java or C++ (my languages of choice).

I thought an experiment was in order. So I tried writing some applications in Python, and then Ruby (well known dynamically typed languages). I was not entirely surprised when I found that type issues simply never arose. My unit tests kept my code on the straight and narrow. I simply didn't need the static type checking that I had depended upon for so many years.

I also realized that the flexibility of dynamically typed langauges makes writing code significantly easier. Modules are easier to write, and easier to change. There are no build time issues at all. Life in a dynamically typed world is fundamentally simpler.

Now I am back programming in Java because the projects I'm working on call for it. But I can't deny that I feel the tug of the dynamically typed languages. I wish I was programming in Ruby or Python, or even Smalltalk.

Does anybody else feel like this? As more and more people adopt test driven development (something I consider to be inevitable) will they feel the same way I do. Will we all be programming in a dynamically typed language in 2010?

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About the Blogger

Robert C. Martin (Uncle Bob) has been a software professional since 1970 and an international software consultant since 1990. He is founder and president of Object Mentor Inc., a team of experienced consultants who mentor their clients worldwide in the fields of C++, Java, OO, Patterns, UML, Agile Methodologies, and Extreme Programming. In 1995 Robert authored the best-selling book: Designing Object Oriented C++ Applications using the Booch Method, published by Prentice Hall. From 1996 to 1999 he was the editor-in-chief of the C++ Report. In 1997 he was chief editor of the book: Pattern Languages of Program Design 3, published by Addison Wesley. In 1999 he was the editor of "More C++ Gems" published by Cambridge Press. He is co-author, with James Newkirk, of "XP in Practice", Addision Wesley, 2001. In 2002 he wrote the long awaited "Agile Software Development: Principles, Patterns, and Practices", Prentice Hall, 2002. He has published many dozens of articles in various trade journals, and is a regular speaker at international conferences and trade shows.