Subtext (programming language)

Schematic tables. An alpha build of the Subtext environment, which illustrates the unique "polymorphic conditionals" present in the IDE.

Subtext is a moderately visual programming language and environment, for writing application software. It is an experimental, research attempt to develop a new programming model, called Example Centric Programming, by treating copied blocks as first class prototypes, for program structure. It uses live text, similar to what occurs in spreadsheets as users update cells, for frequent feedback. It is intended to eventually be developed enough to become a practical language for daily use. It is planned to be open software; the license is not yet determined.

Subtext was created by Jonathan Edwards who submitted a paper on the language to OOPSLA. It was accepted as part of the 2005 conference.

Coherence

A continuation and subset of the Subtext language using other principles, is Coherence, an experimental programming language and environment, which uses a new model of change-driven computation called "Coherent reaction", to coordinate the effects and side-effects of programs interactively as they are being developed. The language is specialized for interactive application software, and is being designed by the creator of Subtext, Jonathan Edwards, who reports upon its development by publishing white papers.

Side effects are both the essence and bane of imperative programming. The programmer must carefully coordinate actions to manage their side effects upon each other. Such coordination is complex, error-prone, and fragile. Coherent reaction is a new model of change-driven computation that coordinates effects automatically. Automatically coordinating actions lets the programmer express what to do, not when to do it.

— Jonathan Edwards, Coherent Reaction, MIT CSAIL

Logo for the Coherence programming language

State changes trigger events called reactions, that in turn change other states. A coherent execution order is one in which each reaction executes before any others that are affected by its changes. A coherent order is discovered iteratively by detecting incoherencies as they occur and backtracking their effects. The fundamental building block of Coherence is the dynamically typed mutable tree. The fundamental abstraction mechanism is the virtual tree, whose value is lazily computed, and whose behavior is generated by coherent reactions.

References

• Example Centric Programming Jonathan Edwards. In OOPSLA October ’04. Describing IDE improvements using advanced UI techniques to present the results of a program during development, instead of the programmer interpreting the program code mentally. Screenshots from a prototype IDE using Eclipse illustrate the techniques with functional examples.
• Subtext: uncovering the simplicity of programming Jonathan Edwards. In OOPSLA October ’05: Proceedings of the 20th annual ACM SIGPLAN conference on Object-oriented programming, systems, languages, and applications.
• Coherent Reaction Jonathan Edwards. In OOPSLA Onward '09. Documents the beginnings of an experimental programming language loosely based upon Subtext, which uses "Coherent reaction", a new model of change-driven computation to coordinate the effects and side-effects of programs automatically. (report)

Cited

External links

Official

• Subtextual.org, official website of Subtext.
• Coherence, official website of Coherence.
• Alarming Development, Weblog for Subtext discussion and debate.

Related

• James Shore: I Want Subtext, the benefits of Subtext and improvements to the schematic tables for abstraction.
• Subtext Info Page, Email list with archives, means to subscribe/unsubscribe.