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variable / @typed/guard

filterMap

Refines and maps a matched value with an Option-returning function.

Package version: 1.0.0-beta.7
Category: Input selection
Since: 1.0.0

Import

import { filterMap } from "@typed/guard";

Signatures

export declare const filterMap: {
    <O, B>(f: (o: O) => Option.Option<B>): <I, R, E>(guard: GuardInput<I, O, E, R>) => Guard<I, B, E, R>;
    <I, O, E, R, B>(guard: GuardInput<I, O, E, R>, f: (o: O) => Option.Option<B>): Guard<I, B, E, R>;
};

Why

Option.none provides a second ordinary non-match stage without introducing typed failure.

Ownership and lifetime

This combinator acquires no resources; the callback runs only for source matches.

Examples

import { filterMap, liftPredicate } from "@typed/guard"
import { Option } from "effect"
const parsed = filterMap(liftPredicate((u: unknown): u is string => typeof u === "string"), (s) => s ? Option.some(Number(s)) : Option.none())

Source