Skip to content

Invariant

The Invariant typeclass is a higher-order abstraction over types that allow mapping the contents of a type in both directions. It is similar to the Covariant typeclass but provides an imap opration, which allows transforming a value in both directions. This typeclass is useful when dealing with data types that can be converted to and from some other types. The imap operation provides a way to convert such data types to other types that they can interact with while preserving their invariants.

4 exports Added in v0.24.0 Source

Do Notation

bindTo

Added in v0.24.0 Source

Signature

declare function bindTo<F extends TypeLambda>(
  F: Invariant<F>,
): {
  <N extends string>(
    name: N,
  ): <R, O, E, A>(self: Kind<F, R, O, E, A>) => Kind<F, R, O, E, { [K in string]: A }>;
  <R, O, E, A, N extends string>(
    self: Kind<F, R, O, E, A>,
    name: N,
  ): Kind<F, R, O, E, { [K in string]: A }>;
};

Other

imapComposition

Added in v0.24.0 Source

Returns a default ternary imap composition.

Signature

declare function imapComposition<F extends TypeLambda, G extends TypeLambda>(
  F: Invariant<F>,
  G: Invariant<G>,
): <FR, FO, FE, GR, GO, GE, A, B>(
  self: Kind<F, FR, FO, FE, Kind<G, GR, GO, GE, A>>,
  to: (a: A) => B,
  from: (b: B) => A,
) => Kind<F, FR, FO, FE, Kind<G, GR, GO, GE, B>>;

tupled

Added in v0.24.0 Source

Convert a value in a singleton array in a given effect.

Signature

declare function tupled<F extends TypeLambda>(
  F: Invariant<F>,
): <R, O, E, A>(self: Kind<F, R, O, E, A>) => Kind<F, R, O, E, [A]>;

Type Class

Invariant interface

Added in v0.24.0 Source

Signature

interface Invariant<F extends TypeLambda> extends TypeClass<F> {
  readonly imap: {
    <A, B>(
      to: (a: A) => B,
      from: (b: B) => A,
    ): <R, O, E>(self: Kind<F, R, O, E, A>) => Kind<F, R, O, E, B>;
    <R, O, E, A, B>(
      self: Kind<F, R, O, E, A>,
      to: (a: A) => B,
      from: (b: B) => A,
    ): Kind<F, R, O, E, B>;
  };
}