Communications of the ACM

Follow us on Twitter at http://twitter.com/blogCACM The Communications Web site, http://cacm.acm.org, features more than a dozen bloggers in the BLOG@CACM community. In each issue of Communications, we’ll publish selected posts or excerpts.

communicate with domain experts and separate problem-specific ideas from the details of general-purpose languages and specific program design decisions.

By “language,” we mean a new syntax, a static semantics, and a dynamic semantics that usually maps the new syntax to elements of the host language and possibly external languages via a foreign-function interface (FFI).

The article does a good job of playing out the issues and possibilities. I’m particularly taken with the explanation of how types play an important role in specifying the new languages. The authors have thought a lot about how a language can usefully constrain and facilitate programmers’ work to improve problem-solving and productivity.

To fit into CACM, the paper is neces-
sarily short, so not all the issues are laid
out. I know from discussions with Krish-
namurthi these ideas started from their
work in education with DrRacket. The
team wanted to define subsets of the
language that were easier to teach, and
generalizing that idea led to this work.

Programmable programming languages have been created in the past. Smalltalk- 72 objects could re-parse their input; the language included an “eyeball” character in methods that could look ahead in the token stream to parse the rest of the input line. Dan Ingalls wrote in the “Smalltalk-80: Bits of History, Words of Advice” that this made Smalltalk- 72 difficult to grow. The programmer was challenged to design a new language that could be understandable by others. How do programmers afterwards know the context and thinking of the programmer who implemented this language? How do they learn “ Smalltalk- 72” when it’s really an umbrella for a bunch of different languages? This modern work is richer for thinking about developing new programming languages for particular problems, but the educational issues are still there.

Programming is not just about problem-solving.

˲ Programming is a job skill. It is hard for students to learn programming. Students often learn a particular programming language to get themselves jobs. Are problem-specific programming languages easier to learn? Will some become so popular and useful that it’s worthwhile (from a job perspective) for a student to learn a problem-specific programming language?

˲ Programming creates infrastructure. Programming is the infrastructure for our world. There are large systems still in use today written in Cobol and PL/1, and we have to maintain that informa-

Mark Guzdial
A Computing Education
Research Perspective
on Programmable
Programming
Languages
http://bit.ly/2JcSr4T
March 8, 2018

When the March Communications appeared in my mailbox, my monthly Blog@CACM post wrote itself. The cover story, an important idea with significant education implications, was A Programmable Programming Language by Matthias Felleisen, Robert Bruce Findler, Matthew Flatt, Shriram Krishnamurthi, Eli Barzilay, Jay McCarthy, and Sam Tobin-Hochstadt. The authors describe their work with Racket, where software developers redesign the programming language to match a problem being solved.

In the ideal world, software developers would analyze each problem in the language of its domain, then articulate solutions in matching terms. They could