make things a little more proper

README.md

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+Propagators
+===========

index.js

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+var _ = require("underscore");
+
+function Scheduler() {
+	var self = {};
+	var propagatorsEverAlerted = [];
+	var alertedPropagators = [];
+
+	self.alertPropagators = function (propagators) {
+		propagatorsEverAlerted = _.union(propagatorsEverAlerted, propagators);
+		alertedPropagators = _.union(alertedPropagators, propagators);
+	};
+
+	self.alertPropagator = function (propagator) {
+		self.alertPropagators([propagator]);
+	};
+
+	self.alertAllPropagators = function () {
+		alertPropagators(propagatorsEverAlerted);
+	};
+
+	self.addPropagator = function (neighbors, toDo) {
+		_.each(neighbors, function (cell) {
+			cell.addNeighbor(toDo);
+		});
+		self.alertPropagator(toDo);
+	}
+
+	self.run = function () {
+		var ticks = 0;
+		while (alertedPropagators.length > 0) {
+			ticks++;
+			alertedPropagators.pop()();
+		}
+		return ticks;
+	};
+
+
+	// (d@ propagator boundary-cell ...)
+	// propagator is a cell containing a propagator constructor for attaching propagators
+	self.diagramApply = function (propagator, boundaryCells) {
+		if (propagator.content()) {
+			propagator.content()(self, boundaryCells);
+		} else {
+			self.addPropagator([propagator], function () {
+				if (propagator.content()) {
+					propagator.content()(self, boundaryCells);
+				}
+			});
+		}
+	};
+
+	// (e@ propagator boundary-cell ...)
+	// like d@, but synthesizes an output cell and returns it
+	self.expressionApply = function (propagator, boundaryCells) {
+		var output = self.Cell();
+		self.diagramApply(propagator, boundaryCells.concat(output));
+		return output;
+	};
+
+	makeCellConstructor();
+	makeDefaultPropagators();
+
+	return self;
+
+	// content is optional
+	function makeCellConstructor() {
+		var scheduler = self;
+		self.Cell = Cell;
+
+		function Cell(content) {
+			var self = {};
+			var neighbors = [];
+			var content = content;
+
+			self.content = function () {
+				return content;
+			};
+
+			self.addContent = function (increment) {
+				var answer = merge(content, increment);
+
+				if (!equivalent(content, answer)) {
+					content = answer;
+					scheduler.alertPropagators(neighbors);
+				}
+			};
+
+			self.addNeighbor = function (neighbor) {
+				neighbors = _.union(neighbors, [neighbor]);
+				scheduler.alertPropagator(neighbor);
+			};
+
+			return self;
+		}
+	}
+
+	function makeDefaultPropagators() {
+		self.pId = functionCallPropagator(requireAll(function (a) { return a }));
+		self.pNot = functionCallPropagator(requireAll(function (a) { return !a }));
+		self.pAdd = functionCallPropagator(requireAll(function (a, b) { return a + b }));
+		self.pSubtract = functionCallPropagator(requireAll(function (a, b) { return a - b }));
+		self.pMultiply = functionCallPropagator(requireAll(function (a, b) { return a * b }));
+		self.pDivide = functionCallPropagator(requireAll(function (a, b) { return a / b }));
+		self.pSwitch = functionCallPropagator(function (control, input) { if (control) return input });
+		self.pConditional = functionCallPropagator(function (control, consequent, alternate) { if (control) { return consequent } else { return alternate } });
+		// TODO: pConditionalRouter
+		// TODO: pDeposit
+		// TODO: pExamine
+		// TODO: pWhen (important!)
+		//   (p:when internal-cells condition-cell body ...)
+		//   when condition-cell is true,
+		//     body: arbitrary collection of code, defining some amount of propagator network that will not be built until the controlling cell indicates that it should
+		//     internal-cells: list of the free variables in body (kluge since can't detect free variables in Scheme)
+		// TODO: pIf
+
+		self.cId = self.Cell(function (scheduler, cells) {
+			scheduler.diagramApply(scheduler.pId, [cells[0], cells[1]]);
+			scheduler.diagramApply(scheduler.pId, [cells[1], cells[0]]);
+		});
+
+		self.cNot = self.Cell(function (scheduler, cells) {
+			scheduler.diagramApply(scheduler.pNot, [cells[0], cells[1]]);
+			scheduler.diagramApply(scheduler.pNot, [cells[1], cells[0]]);
+		});
+
+		self.cAdd = self.Cell(function (scheduler, cells) {
+			scheduler.diagramApply(scheduler.pAdd,      [cells[0], cells[1], cells[2]]);
+			scheduler.diagramApply(scheduler.pSubtract, [cells[2], cells[1], cells[0]]);
+			scheduler.diagramApply(scheduler.pSubtract, [cells[2], cells[0], cells[1]]);
+		});
+		self.cSubtract = self.Cell(function (scheduler, cells) {
+			scheduler.diagramApply(scheduler.cAdd,      [cells[1], cells[2], cells[0]]);
+		});
+
+		self.cMultiply = self.Cell(function (scheduler, cells) {
+			scheduler.diagramApply(scheduler.pMultiply, [cells[0], cells[1], cells[2]]);
+			scheduler.diagramApply(scheduler.pDivide,   [cells[2], cells[1], cells[0]]);
+			scheduler.diagramApply(scheduler.pDivide,   [cells[2], cells[0], cells[1]]);
+		});
+		self.cDivide = self.Cell(function (scheduler, cells) {
+			scheduler.diagramApply(scheduler.cMultiply, [cells[1], cells[2], cells[0]]);
+		});
+
+		function requireAll(f) {
+			return function () {
+				if (_.all(arguments, function (value) { return value != undefined })) {
+					return f.apply(this, arguments);
+				}
+			};
+		}
+
+		function functionCallPropagator(f) {
+			return self.Cell(function (scheduler, cells) {
+				var inputs = cells.slice(0, cells.length - 1);
+				var output = cells[cells.length - 1];
+				scheduler.addPropagator(inputs, toDo);
+
+				function toDo() {
+					var answer = f.apply(undefined, _.map(inputs, getContent));
+					output.addContent(answer);
+
+					function getContent(cell) {
+						return cell.content();
+					}
+				}
+			});
+		}
+	}
+}
+
+// function addCompoundPropagator(scheduler, neighbors, toBuild) {
+// 	var done = false;
+// 	scheduler.addPropagator(neighbors, toDo);
+
+// 	function toDo() {
+// 		if (!done) {
+// 			if (_.any(neighbors, getContent)) {
+// 				done = true;
+// 				toBuild();
+// 			}
+// 		}
+
+// 		function getContent(cell) {
+// 			return cell.content();
+// 		}
+// 	}
+// }
+
+function merge(content, increment) {
+	if (increment == undefined) {
+		return content;
+	} else {
+		return increment; // TODO
+	}
+}
+
+function equivalent(a, b) {
+	return a === b;
+}
+
+exports.Scheduler = Scheduler;

package.json

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+{
+	"name" : "propagators",
+	"description" : "implementation of propagators http://groups.csail.mit.edu/mac/users/gjs/propagators/",
+	"license" : "MIT",
+	"author" : "Tom Lieber <[email protected]>",
+	"version" : "0.0.1",
+	"main" : "./index",
+	"repository" : {
+		"type" : "git",
+		"url" : "https://github.com/alltom/propagators.git"
+	},
+	"dependencies" : {
+		"underscore" : "~1.5.2"
+	},
+	"devDependencies" : {
+		"tap" : "~0.4.6"
+	},
+	"scripts" : {
+		"test" : "tap test/test-*.js"
+	}
+}