An educational pure functional programming library in TypeScript
Improve type safety in interruptFiber and document pattern matching casts
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src/index.ts
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src/index.ts
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(value: Extract<T, { _tag: K }>) => R
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}
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/** Exhaustive pattern matching on tagged unions */
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export const match = <T extends { _tag: string }>(value: T) =>
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<R>(patterns: Pattern<T, R>): R =>
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/**
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* Exhaustive pattern matching on tagged unions.
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*
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* The `any` cast is safe because Pattern<T, R> requires handlers for all variants,
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* and we index by the actual _tag value which TypeScript has already narrowed.
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*/
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export const match = <T extends { _tag: string }>(value: T) =>
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<R>(patterns: Pattern<T, R>): R =>
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patterns[value._tag as keyof typeof patterns](value as any)
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/** Match with wildcard fallback */
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export const matchOr = <T extends { _tag: string }, R>(defaultValue: R) =>
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(value: T) =>
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(patterns: Partial<Pattern<T, R>>): R =>
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/**
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* Match with wildcard fallback for partial pattern matching.
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*
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* The `any` cast is safe because we use optional chaining and fall back to defaultValue
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* when the handler is undefined.
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*/
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export const matchOr = <T extends { _tag: string }, R>(defaultValue: R) =>
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(value: T) =>
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(patterns: Partial<Pattern<T, R>>): R =>
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(patterns[value._tag as keyof typeof patterns] as any)?.(value) ?? defaultValue
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/** Predicate-based matching */
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({ _tag: "Fork", effect }) as Eff<Fiber<A, E>, never, R>
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/** Interrupt a fiber */
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export const interruptFiber = (fiber: Fiber<any, any>): Eff<void, never, unknown> =>
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export const interruptFiber = <A, E>(fiber: Fiber<A, E>): Eff<void, never, unknown> =>
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async((resume) => {
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fiber.interrupt().then(() => resume(Exit.succeed(undefined)))
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})