name: effect-facet-predicate-combinators
description: Guidance for facet effect/Predicate#combinators focused on APIs like compose. Load after effect-skill-router when this facet is the primary owner.
Effect Facet Predicate#combinators
Owned scope
- Owns only
effect/Predicate#combinators.
- Parent module:
effect/Predicate.
What it is for
- logical predicate composition. Predicate and Refinement helpers for runtime checks, filtering, and type narrowing. This module provides small, pure functions you can combine to decide whether a value matches a condition and, when using refinements, narrow TypeScript types.
API quick reference
compose- Full API list:
references/api-reference.md
How to use it
- Keep work focused on the
combinators concern for effect/Predicate.
- Prefer pipe-based composition to keep transformations explicit and testable.
- Use the reference docs to select the smallest API surface that solves your task.
- Validate behavior against existing tests before introducing new usage patterns.
Starter example
import * as Predicate from "effect/Predicate";
const isPositive = (n: number) => n > 0;
const data = [2, -1, 3];
console.log(data.filter(isPositive));
Common pitfalls
- Prefer explicit, typed combinators over ad-hoc casting or unchecked assumptions.
Not covered here
- Sibling facets under the same parent are out of scope:
effect-facet-predicate-core (effect/Predicate#core)effect-facet-predicate-guards (effect/Predicate#guards)
- Parent module ownership belongs to
effect-module-predicate.
Escalate to
effect-module-predicate for parent module-wide workflows.effect-skill-router for cross-module routing and ownership checks.
Reference anchors
- Parent tests:
packages/effect/test/Predicate.test.ts
- Parent tests:
packages/effect/test/Iterable.test.ts
- API details:
references/api-reference.md
- Usage notes:
references/usage-reference.md
- Ownership mapping:
references/owner.md
By