effect-io-ai

Package: effect
Module: Match

Match.not

Creates a pattern that excludes a specific value while allowing all others.

When to use

Use to add a negative pattern case for inputs that should match when another pattern does not.

Details

Any excluded value bypasses the provided function and continues matching through later cases.

Example (Ignoring a specific value)

import { Match } from "effect"

// Create a matcher for string or number values
const match = Match.type<string | number>().pipe(
  // Match any value except "hi", returning "ok"
  Match.not("hi", () => "ok"),
  // Fallback case for when the value is "hi"
  Match.orElse(() => "fallback")
)

console.log(match("hello"))
// Output: "ok"

console.log(match("hi"))
// Output: "fallback"

See

• when for adding a positive pattern case

Signature

declare const not: <R, const P extends Types.PatternPrimitive<R> | Types.PatternBase<R>, Ret, Fn extends (_: Types.NotMatch<R, P>) => Ret>(pattern: P, f: Fn) => <I, F, A, Pr>(self: Matcher<I, F, R, A, Pr, Ret>) => Matcher<I, Types.AddOnly<F, Types.WhenMatch<R, P>>, Types.ApplyFilters<I, Types.AddOnly<F, Types.WhenMatch<R, P>>>, A | ReturnType<Fn>, Pr, Ret>

Source

Since v4.0.0