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e897ca7848
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f432f7796c
| Author | SHA1 | Date | |
|---|---|---|---|
| f432f7796c | |||
| ebc3f07610 | |||
| 773fcc7ef3 |
@ -7,7 +7,7 @@
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"quoteStyle": "alwaysSingle",
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"trailingCommas": "onlyMultiLine",
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"operatorPosition": "nextLine",
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"arrowFunction.useParentheses": "preferNone",
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"arrowFunction.useParentheses": "maintain",
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"binaryExpression.linePerExpression": false,
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"memberExpression.linePerExpression": false,
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"bracePosition": "sameLineUnlessHanging",
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@ -1,28 +1,28 @@
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export type Left<E> = {readonly _tag: 'Left', readonly left: E}
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export type Right<A> = {readonly _tag: 'Right', readonly right: A}
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export type Either<E, A> = Left<E> | Right<A>
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export type Either<A, E> = Right<A> | Left<E>
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// Constructors
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export const left = <E>(e: E): Either<E, never> => ({
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export const left = <E>(e: E): Either<never, E> => ({
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_tag: 'Left',
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left: e,
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})
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export const right = <A>(a: A): Either<never, A> => ({
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export const right = <A>(a: A): Either<A, never> => ({
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_tag: 'Right',
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right: a,
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})
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// Operations
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export const eitherMap =
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<E, A, B>(f: (a: A) => B) => (fa: Either<E, A>): Either<E, B> =>
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<E, A, B>(f: (a: A) => B) => (fa: Either<A, E>): Either<B, E> =>
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fa._tag === 'Right' ? right(f(fa.right)) : fa
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export const eitherChain =
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<E, A, B>(f: (a: A) => Either<E, B>) =>
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(fa: Either<E, A>): Either<E, B> =>
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<E, A, B>(f: (a: A) => Either<B, E>) =>
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(fa: Either<A, E>): Either<B, E> =>
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fa._tag === 'Right' ? f(fa.right) : fa
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export const fold =
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<E, A, B>(onLeft: (e: E) => B, onRight: (a: A) => B) =>
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(fa: Either<E, A>): B =>
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<A, B, E>(onLeft: (e: E) => B, onRight: (a: A) => B) =>
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(fa: Either<A, E>): B =>
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fa._tag === 'Left' ? onLeft(fa.left) : onRight(fa.right)
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