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. | ” |
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—Jonathan Edwards, Coherent Reaction, MIT CSAIL |
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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.
Read more about this topic: Subtext (programming Language)
Famous quotes containing the word coherence:
“Art and ideology often interact on each other; but the plain fact is that both spring from a common source. Both draw on human experience to explain mankind to itself; both attempt, in very different ways, to assemble coherence from seemingly unrelated phenomena; both stand guard for us against chaos.”
—Kenneth Tynan (1927–1980)
“Twentieth-century art may start with nothing, but it flourishes by virtue of its belief in itself, in the possibility of control over what seems essentially uncontrollable, in the coherence of the inchoate, and in its ability to create its own values.”
—A. Alvarez (b. 1929)
“When the coherence of the parts of a stone, or even that composition of parts which renders it extended; when these familiar objects, I say, are so inexplicable, and contain circumstances so repugnant and contradictory; with what assurance can we decide concerning the origin of worlds, or trace their history from eternity to eternity?”
—David Hume (1711–1776)