The A-Z of Programming Languages: D

Walter Bright talks about D and his desire to improve on systems programming languages.

Computerworld is undertaking a series of investigations into the most widely-used programming languages. Previously we have spoken to Alfred v. Aho of AWK fame, S. Tucker Taft on the Ada 1995 and 2005 revisions, Microsoft about its server-side script engine ASP, Chet Ramey about his experience maintaining Bash, Bjarne Stroustrup of C++ fame, to Charles H. Moore about the design and development of Forth, a chat with the irreverent Don Woods about the development and uses of INTERCAL, Stephen C. Johnson on YACC and most recently Modula-3 design committee member, Luca Cardelli.

In this interview, we chat to Walter Bright about D and his desire to improve on systems programming languages. According to his home page, Bright was trained as a mechanical engineer, and has worked for Boeing on the 757 stabilizer trim system. Ever since this experience however, he has been writing software, and has a particular interest in compilers.

Please note that we are no longer following exact alphabetical order for this series, due to popular demand. If you'd like to submit any suggestions for programming languages or language authors that you'd like to see covered, please email naomi@computerworld.com.au.

What prompted the development of D?

Being a compiler developer, there's always at the back of my mind the impetus for applying what I know to design a better language. At my core I'm an engineer, and never can look at anything without thinking of ways to improve it.

The tipping point came in 1999 when I left Symantec and found myself at a crossroads. It was the perfect opportunity to put into practice what I'd been thinking about for many years.

Was there a particular problem you were trying to solve?

There was no specific problem. I'd been writing code in C++ for 12 years, and had written a successful C++ compiler. This gave me a fairly intimate knowledge of how the language worked and where the problems were.

C++ was (and is) limited by the requirement of legacy compatibility, and I thought much could be done if that requirement was set aside. We could have the power of C++ with the hindsight to make it beautiful.

I had also been programming in other languages, which had a lot to contribute.

How did the name D come about?

It started out as the Mars programming language (as the company name is Digital Mars). But my friends and colleagues kept calling it D, as it started out as a re-engineering of C++, and eventually the name stuck.

Why did you feel that C++ needed re-engineering?

A lot has been learned about programming since C++ was developed. Much of this has been folded in C++ as layers on top of the existing structure, to maintain backwards compatibility. It's like a farmhouse that has been added on to by successive generations, each trying to modernize it and adapting it to their particular needs. At some point, with a redesign, you can achieve what is needed directly.

But D today has moved well beyond that. Many successful concepts from other languages like JavaScript, PERL, Ruby, Lisp, Ada, Erlang, Python, etc., have had a significant influence on D.

What elements of C++ have you kept, and what elements have you deliberately discarded?

D keeps enough so that a C++ programmer would feel immediately comfortable programming in D. Obsolete technologies like the preprocessor have been replaced with modern systems, such as modules. Probably the central thing that has been kept is the idea that D is a systems programming language, and the language always respects that ultimately the programmer knows best.

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