Designing DSLs

Hello and welcome to a new series of blogs called “Designing DSLs” or DDSL for short. If you have used or designed a DSL before, then you’ll know that there are a couple of pitfalls. This blog series aims to provide tips how to build “great” DSLs – whatever that might be ;-)

What are the most common pitfalls for designers of DSLs?

  • The DSL is too broad
  • The DSL is too limited
  • The syntax has weird quirks (a.k.a. backwards compatibility syndrome)

Why is it so hard to design a great DSL? They should be simple, right?

Well, as Einstein (“Everything should be made as simple as possible, but no simpler“) and Blaise Pascal (“I would have written a shorter letter, but I did not have the time.“) already knew, it’s always easy to make something complicated – simplicity is hard.

On top of that, every mathematical system is either incomplete or inconsistent. And let’s not forget that each DSL is a model, too. And as you might know, all models are wrong but some are useful.

Should we abandon all hope? No. Just always remember that a good DSL is hard work.

First, a general tip: Look at existing examples. There are thousands of examples out there; use them. Knowing several programming languages yourself is a big bonus (everyone should know more than two languages).

“Wait a minute,” I hear you ask, “these are real programming languages!” So? A lot of brainpower went into designing them (or working around shortcomings), which makes them a great source of inspiration. Bonus: A lot of people know these languages which gives you a larger audience to discuss ideas (as opposed to the 3-4 people who will use your DSL in the beginning).

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