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import { assertEquals } from "https://deno.land/std@0.65.0/testing/asserts.ts";
import { assertIsDefined, assertIsEquivalent, assertIsNone } from "./asserts.js";import { factorizeSumType } from "./SumType.js";
const $$value = Symbol.for("TypeValue");
export const Maybe = factorizeSumType(  "Maybe",  {    Nothing: [],    Just: [ $$value ]  });
Maybe.fromNullable = value => !assertIsDefined(value) || assertIsNone(value) ? Maybe.nothing() : Maybe.just(value);Maybe.just = value => Maybe.Just(value);Maybe.nothing = () => Maybe.Nothing;Maybe.of = value => Maybe.Just(value);
// filter :: Maybe a => a ~> (a -> Boolean) -> aMaybe.prototype.filter = function (composedFunction) {
  return Maybe.fromNullable(composedFunction(this[$$value]) ? this[$$value] : null)[$$value] || null;};
// map :: Maybe a => a ~> (a -> b) -> Maybe bMaybe.prototype.map = function (composedFunction) {
  return (Maybe.Just.is(this)) ? Maybe.Just(composedFunction(this[$$value])) : this;};
Deno.test(  "Maybe: #just",  () =>      assertIsEquivalent(Maybe.just(42), Maybe.Just(42)));
Deno.test(  "Maybe.Just: #map",  () =>    assertIsEquivalent(      Maybe.Just(42).map(x => x * 2),      Maybe.Just(84)    ));
Deno.test(  "Maybe.Just: #map - Identity",  () => {    const container = Maybe.Just(42);
    assertIsEquivalent(      container.map(x => x),      container    );  });
Deno.test(  "Maybe.Just: #map - Composition",  () => {    const container = Maybe.Just(42);    const f = x => x + 2;    const g = x => x * 2;
    assertIsEquivalent(      container.map(f).map(g),      container.map(x => g(f(x)))    );  });
Deno.test(  "Maybe.Nothing: #map",  () =>    assertIsEquivalent(      Maybe.Nothing.map(x => x * 2),      Maybe.Nothing    ));
Deno.test(  "Maybe.Nothing: #map - Identity",  () => {    const container = Maybe.Nothing;
    assertIsEquivalent(      container.map(x => x),      container    );  });
Deno.test(  "Maybe.Nothing: #map - Composition",  () => {    const container = Maybe.Nothing;    const f = x => x + 2;    const g = x => x * 2;
    assertIsEquivalent(      container.map(f).map(g),      container.map(x => g(f(x)))    );  });
Deno.test(  "Maybe.Just: #filter",  () => {    assertEquals(      Maybe.Just(42).filter(x => x % 2 === 0),      42    );    assertEquals(      Maybe.Just(9).filter(x => x % 2 === 0),      null    );  });
Deno.test(  "Maybe.Nothing: #filter",  () =>    assertEquals(      Maybe.Nothing.filter(x => x % 2 === 0),      null    ));
Deno.test(  "Maybe: Test #fold",  () => {    const serialize = (container) =>      container.fold({        Nothing: () => "There is no value.",        Just: (value) => `The value is ${value}.`      });    const container = Maybe.Just(42);
    assertEquals(      serialize(container),      "The value is 42."    );  });
export default Maybe;