Object

Use QueryLogic.UNKNOWABLE to signal that no answer to the problem can be figured out.

Consider the following difference:

import {QueryLogic} from "can";

const queryLogic = new QueryLogic();

const diff = queryLogic.difference({
  filter: {age: 35},
  sort: "name"
},{
  filter: {name: "Justin"},
  sort: "age"
});
// Codepen logs limited nesting of objects.
// Using JSON.stringify to circumvent issue.
console.log( JSON.stringify( diff ) ); //-> "{
//   'filter': {
//     'age': '35',
//     'name': {'$ne': 'Justin'}
//   },
//   'sort': 'name'
// }"

Since it is possible that there might be records in the first set that won't be in the second set, thus difference it returns a query.

Now consider a similar example, but with pagination added:

import {QueryLogic} from "can";

const queryLogic = new QueryLogic();

const diff = queryLogic.difference({
  filter: {age: 35},
  sort: "name",
  page: {start: 0, end: 10}
},{
  filter: {name: "Justin"},
  sort: "age",
  page: {start: 0, end: 12}
});
console.log( diff ); //-> QueryLogic.UNKNOWABLE

Because we added pagination, the answer should paginated data in the result. This means we would have to know what the actual data set looked like to make a determination if the value was EMPTY or UNDEFINABLE. Because we don't have the actual data set, we return UNKNOWABLE.

Think of:

• UNDEFINABLE as representing a set between EMPTY and UNIVERSAL
• UNKNOWABLE as a set that could be EMPTY, UNIVERSAL or anywhere between.