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effect

Invariant overview

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.

Added in v0.24.0

Table of contents

do notation

bindTo

Signature

export declare const 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 N]: A }>
  <R, O, E, A, N extends string>(self: Kind<F, R, O, E, A>, name: N): Kind<F, R, O, E, { [K in N]: A }>
}

Added in v0.24.0

type class

Invariant (interface)

Signature

export 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>
  }
}

Added in v0.24.0

utils

imapComposition

Returns a default ternary imap composition.

Signature

export declare const 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>>

Added in v0.24.0

tupled

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

Signature

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

Added in v0.24.0