props
Contains a collection of prop generating functions.
The following functions create compares objects that can be mixed together to create a set Algebra.
var set = require("can-set");
var algebra = new set.Algebra(
  {
    // ignore this property in set algebra
    sessionId:  function(){ return true }
  },
  set.props.boolean("completed"),
  set.props.rangeInclusive("start","end")
);