Implement TaskEither.bimap from EitherT.bimap

Author: teves-castro

src/EitherT.ts

@@ -85,6 +85,21 @@ export function mapLeft<F>(
   return f => fa => F.map(fa, e => e.mapLeft(f))
 }
 
+export function bimap<F extends URIS2>(
+  F: Functor2<F>
+): <M, L, V, A, B>(fa: Type2<F, M, Either<L, A>>, f: (l: L) => V, g: (a: A) => B) => Type2<F, M, Either<V, B>>
+export function bimap<F extends URIS>(
+  F: Functor1<F>
+): <L, V, A, B>(fa: Type<F, Either<L, A>>, f: (l: L) => V, g: (a: A) => B) => Type<F, Either<V, B>>
+export function bimap<F>(
+  F: Functor<F>
+): <L, V, A, B>(fa: HKT<F, Either<L, A>>, f: (l: L) => V, g: (a: A) => B) => HKT<F, Either<V, B>>
+export function bimap<F>(
+  F: Functor<F>
+): <L, V, A, B>(fa: HKT<F, Either<L, A>>, f: (l: L) => V, g: (a: A) => B) => HKT<F, Either<V, B>> {
+  return (fa, f, g) => F.map(fa, e => e.bimap(f, g))
+}
+
 export function getEitherT<M extends URIS2>(M: Monad2<M>): EitherT2<M>
 export function getEitherT<M extends URIS>(M: Monad1<M>): EitherT1<M>
 export function getEitherT<M>(M: Monad<M>): EitherT<M>

src/TaskEither.ts

@@ -20,6 +20,7 @@ export type URI = typeof URI
 
 const eitherTfold = eitherT.fold(task.task)
 const eitherTmapLeft = eitherT.mapLeft(task.task)
+const eitherTbimap = eitherT.bimap(task.task)
 
 /**
  * @data
@@ -60,7 +61,7 @@ export class TaskEither<L, A> {
     return new TaskEither(this.value.chain(e => e.fold(l => f(l).value, a => eitherTTask.of(a))))
   }
   bimap<V, B>(f: (l: L) => V, g: (a: A) => B): TaskEither<V, B> {
-    return new TaskEither(this.value.map(e => e.bimap(f, g)))
+    return new TaskEither(eitherTbimap(this.value, f, g))
   }
 }