Module boolean

Boolean shape types and operations.

Defines the shape describing the truth values a resource may carry and provides the boolean factory stating it, mapping the JSON boolean type to the XSD 1.0 boolean datatype. The kind closes the domain to two values; an enumeration closes it further to one, so that a member may stand as the tag telling the alternatives of a union apart.

¹ XSD 1.0 datatypes are referenced by RDF 1.1 and JSON-LD 1.1 as normative

Compatibility

¹ Canonical form: true, false

Defining boolean shapes

import { boolean } from '@metreeca/blue/boolean';

const flag = boolean();                 // either truth value
const settled = boolean({ in: true });  // the single admitted value
const paid = boolean(true);             // the same, stated as a bare value
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Using in resource shapes

import { optional, required, resource } from '@metreeca/blue/resource';
import { boolean } from '@metreeca/blue/boolean';

const Product = resource({
  available: required(boolean()),
  featured: optional(boolean())
});
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Tagging the alternatives of a union

import { boolean } from '@metreeca/blue/boolean';
import { date } from '@metreeca/blue/string';
import { required, resource } from '@metreeca/blue/resource';
import { union } from '@metreeca/blue/union';

const Payment = union(
  resource({ settled: required(boolean(false)), due: required(date()) }),
  resource({ settled: required(boolean(true)), paid: required(date()) })
);
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A stored value states one truth value, singling out the alternative it belongs to, and the type of the value the union describes is narrowed by the tag exactly as the shape is.