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/**
* Works with values that may be `undefined`.
*
* Use this module for plain TypeScript values of type `A | undefined` when
* `undefined` is the only absence marker. It is a small alternative to wrapping
* values in `Option` when your data already uses `undefined` to mean "no
* value". The module includes helpers for mapping defined values, matching both
* cases, throwing when a value is missing, adapting throwing functions, and
* building reducers or combiners.
*
* @since 4.0.0
*/
import * as Combiner from "./Combiner.ts";
import type { LazyArg } from "./Function.ts";
import * as Reducer from "./Reducer.ts";
/**
* Maps a defined value with `f`, or returns `undefined` unchanged.
*
* **When to use**
*
* Use to apply a pure transformation to an `A | undefined` value while
* preserving `undefined` as absence.
*
* @see {@link match} when you need to handle the `undefined` case explicitly
*
* @category mapping
* @since 4.0.0
*/
export declare const map: {
/**
* Maps a defined value with `f`, or returns `undefined` unchanged.
*
* **When to use**
*
* Use to apply a pure transformation to an `A | undefined` value while
* preserving `undefined` as absence.
*
* @see {@link match} when you need to handle the `undefined` case explicitly
*
* @category mapping
* @since 4.0.0
*/
<A, B>(f: (a: A) => B): (self: A | undefined) => B | undefined;
/**
* Maps a defined value with `f`, or returns `undefined` unchanged.
*
* **When to use**
*
* Use to apply a pure transformation to an `A | undefined` value while
* preserving `undefined` as absence.
*
* @see {@link match} when you need to handle the `undefined` case explicitly
*
* @category mapping
* @since 4.0.0
*/
<A, B>(self: A | undefined, f: (a: A) => B): B | undefined;
};
/**
* Pattern matches on an `A | undefined` value, running `onDefined` when the
* value is present or evaluating `onUndefined` when the value is `undefined`.
*
* **When to use**
*
* Use when you need to turn an `A | undefined` into a non-optional result by
* handling both the defined and undefined branches in one expression.
*
* @see {@link map} for transforming defined values while preserving `undefined`
* @see {@link getOrThrowWith} for throwing when the value is `undefined` instead of returning a fallback branch
*
* @category pattern matching
* @since 4.0.0
*/
export declare const match: {
/**
* Pattern matches on an `A | undefined` value, running `onDefined` when the
* value is present or evaluating `onUndefined` when the value is `undefined`.
*
* **When to use**
*
* Use when you need to turn an `A | undefined` into a non-optional result by
* handling both the defined and undefined branches in one expression.
*
* @see {@link map} for transforming defined values while preserving `undefined`
* @see {@link getOrThrowWith} for throwing when the value is `undefined` instead of returning a fallback branch
*
* @category pattern matching
* @since 4.0.0
*/
<B, A, C = B>(options: {
readonly onUndefined: LazyArg<B>;
readonly onDefined: (a: A) => C;
}): (self: A | undefined) => B | C;
/**
* Pattern matches on an `A | undefined` value, running `onDefined` when the
* value is present or evaluating `onUndefined` when the value is `undefined`.
*
* **When to use**
*
* Use when you need to turn an `A | undefined` into a non-optional result by
* handling both the defined and undefined branches in one expression.
*
* @see {@link map} for transforming defined values while preserving `undefined`
* @see {@link getOrThrowWith} for throwing when the value is `undefined` instead of returning a fallback branch
*
* @category pattern matching
* @since 4.0.0
*/
<A, B, C = B>(self: A | undefined, options: {
readonly onUndefined: LazyArg<B>;
readonly onDefined: (a: A) => C;
}): B | C;
};
/**
* Returns the defined value, or throws the value produced by `onUndefined`
* when the input is `undefined`.
*
* **When to use**
*
* Use when you need fail-fast unwrapping of an `A | undefined` value and want
* to provide the thrown error for the undefined case.
*
* **Details**
*
* Defined values are returned unchanged. When the input is `undefined`,
* `onUndefined` is called and its result is thrown.
*
* @see {@link getOrThrow} for the default-error sibling
* @see {@link match} for handling defined and undefined cases without throwing
*
* @category getters
* @since 4.0.0
*/
export declare const getOrThrowWith: {
/**
* Returns the defined value, or throws the value produced by `onUndefined`
* when the input is `undefined`.
*
* **When to use**
*
* Use when you need fail-fast unwrapping of an `A | undefined` value and want
* to provide the thrown error for the undefined case.
*
* **Details**
*
* Defined values are returned unchanged. When the input is `undefined`,
* `onUndefined` is called and its result is thrown.
*
* @see {@link getOrThrow} for the default-error sibling
* @see {@link match} for handling defined and undefined cases without throwing
*
* @category getters
* @since 4.0.0
*/
(onUndefined: () => unknown): <A>(self: A | undefined) => A;
/**
* Returns the defined value, or throws the value produced by `onUndefined`
* when the input is `undefined`.
*
* **When to use**
*
* Use when you need fail-fast unwrapping of an `A | undefined` value and want
* to provide the thrown error for the undefined case.
*
* **Details**
*
* Defined values are returned unchanged. When the input is `undefined`,
* `onUndefined` is called and its result is thrown.
*
* @see {@link getOrThrow} for the default-error sibling
* @see {@link match} for handling defined and undefined cases without throwing
*
* @category getters
* @since 4.0.0
*/
<A>(self: A | undefined, onUndefined: () => unknown): A;
};
/**
* Returns the defined value, or throws a default `Error` when the input is
* `undefined`.
*
* **When to use**
*
* Use when you need to unwrap a value that should already be defined and a
* generic missing-value `Error` is acceptable.
*
* **Details**
*
* Defined inputs are returned unchanged. `undefined` throws
* `new Error("getOrThrow called on a undefined")`.
*
* @see {@link getOrThrowWith} for the sibling that lets callers choose the thrown value
* @see {@link match} for handling defined and undefined cases without throwing
*
* @category getters
* @since 4.0.0
*/
export declare const getOrThrow: <A>(self: A | undefined) => A;
/**
* Converts a throwing function into one that returns successful results
* unchanged and returns `undefined` when the function throws.
*
* **When to use**
*
* Use to adapt exception-throwing functions when `undefined` is the absence
* value you want to return for failures.
*
* **Gotchas**
*
* Thrown values are discarded. If the wrapped function can successfully return
* `undefined`, that success is indistinguishable from a thrown failure.
*
* @category converting
* @since 4.0.0
*/
export declare const liftThrowable: <A extends ReadonlyArray<unknown>, B>(f: (...a: A) => B) => (...a: A) => B | undefined;
/**
* Creates a `Reducer` for `UndefinedOr<A>` that prioritizes the first non-`undefined`
* value and combines values when both operands are present.
*
* **When to use**
*
* Use when you need to reduce values that may be `undefined`, keeping the
* first defined value as a fallback and combining only when both operands are
* defined.
*
* **Details**
*
* Combining `undefined` with `undefined` returns `undefined`. Combining a
* defined value with `undefined` keeps the defined value, so the first defined
* value wins when only one side is present. When both values are defined, they
* are combined with `combiner.combine`. The reducer's initial value is
* `undefined`.
*
* @category constructors
* @since 4.0.0
*/
export declare function makeReducer<A>(combiner: Combiner.Combiner<A>): Reducer.Reducer<A | undefined>;
/**
* Creates a `Combiner` for `A | undefined` that combines values only when both
* operands are defined.
*
* **When to use**
*
* Use to lift a `Combiner` so any `undefined` operand makes the combined result
* `undefined`.
*
* **Details**
*
* - `undefined` combined with any value returns `undefined`
* - Any value combined with `undefined` returns `undefined`
* - `a` combined with `b` returns `combiner.combine(a, b)`
*
* @see {@link makeReducerFailFast} if you have a `Reducer` and want to lift it
* to `UndefinedOr` values.
*
* @category constructors
* @since 4.0.0
*/
export declare function makeCombinerFailFast<A>(combiner: Combiner.Combiner<A>): Combiner.Combiner<A | undefined>;
/**
* Creates a `Reducer` for `A | undefined` by wrapping an existing reducer with
* fail-fast semantics.
*
* **When to use**
*
* Use to wrap an existing `Reducer` so any `undefined` value aborts the entire
* reduction result.
*
* **Details**
*
* - Initial value is the wrapped reducer's `initialValue`
* - Combining two defined values delegates to the wrapped reducer
* - If the accumulator or next value is `undefined`, the reduction returns `undefined`
*
* @see {@link makeCombinerFailFast} if you only have a `Combiner` and want to
* lift it to `UndefinedOr` values.
*
* @category constructors
* @since 4.0.0
*/
export declare function makeReducerFailFast<A>(reducer: Reducer.Reducer<A>): Reducer.Reducer<A | undefined>;
//# sourceMappingURL=UndefinedOr.d.ts.map

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