Domain-specific languages

As program­mers, the idea of language-oriented program­ming may be new. But we’ve been using special-purpose languages—known as domain-specific languages (aka DSLs)—for a long time.

What qual­i­fies as a DSL? A nota­tional sys­tem for cer­tain data, or oper­a­tions on data, tailored to the needs of a partic­ular set of prob­lems.

Even if the termi­nology is new, DSLs are estab­lished in program­ming prac­tice. For the details, see Why Language-Oriented Program­ming? Why Racket?

Common DSLs

When first presented with the idea of a DSL, a contrarian colleague will likely inter­ject: “Use a DSL? We’ve never done that before.”

The response: “Of course we have. For instance—”

awk text-processing utility on Unix-like oper­ating systems

bash shell program on Unix-like oper­ating systems

Coq language for proving math­e­mat­ical theo­rems

CSS format for storing & relating visual-styling instruc­tions for web pages

HDL a cate­gory of languages for modeling hard­ware compo­nents

.htac­cess config­u­ra­tion language for Apache web servers

HTML markup language for web docu­ments

Julia language for scien­tific & tech­nical computing

lex/yacc tools for making tokenizers & parsers

make tool for config­uring soft­ware builds

MATLAB language for scien­tific & tech­nical computing

Post­Script page-descrip­tion language

printf embedded language for format­ting strings

R language for statis­tical computing

regular expres­sions embedded language for matching strings

SQL language for data­base access and manage­ment

TeX high-level page-descrip­tion language

XML markup language, typi­cally for docu­ments

Racket-imple­mented DSLs

Temporarily molli­fied, the contrarian colleague will then say “OK, a DSL is not such a crazy idea. But why should we use Racket to make a DSL? Who’s ever done that?”

The response: “Many have. For instance—”

Anatomy language for gener­ating animal skele­tons, espe­cially dinosaurs

bookcover language for gener­ating PDF book covers

brag language for gener­ating parsers from BNF gram­mars

datalog language for logic program­ming

Heresy Lisp with BASIC-inspired syntax

Pollen language for making digital books (like this one)

Pyramid Scheme language for creating Ethereum smart contracts (also, best name ever)

Rex alter­na­tive syntax for spec­i­fying regular languages

Rosette language for creating program veri­fi­ca­tion and synthesis tools

Scribble language for gener­ating Racket docu­men­ta­tion

Slideshow language for gener­ating inter­ac­tive slide presen­ta­tions

shill scripting language with priv­i­lege controls

web-server language for making web appli­ca­tions

And more to come

If you release a Racket-imple­mented domain-specific language as a conse­quence of what you’ve learned in Beau­tiful Racket, let me know—I’ll be happy to add it to this page.