in src/lib/vpsc.js [89:93]
Variable.prototype.visitNeighbours = function (prev, f) {
var ff = function (c, next) { return c.active && prev !== next && f(c, next); };
this.cOut.forEach(function (c) { return ff(c, c.right); });
this.cIn.forEach(function (c) { return ff(c, c.left); });
};