<A>(self: Predicate<A>): Predicate<A>Negates a predicate.
When to use
Use when you want the inverse of an existing predicate.
Details
Returns a new predicate that flips the boolean result.
Example (Negating a predicate)
import { Predicate } from "effect"
const isNotString = Predicate.not(Predicate.isString)
console.log(isNotString(1))export function function not<A>(
self: Predicate<A>
): Predicate<A>
Negates a predicate.
When to use
Use when you want the inverse of an existing predicate.
Details
Returns a new predicate that flips the boolean result.
Example (Negating a predicate)
import { Predicate } from "effect"
const isNotString = Predicate.not(Predicate.isString)
console.log(isNotString(1))
not<function (type parameter) A in not<A>(self: Predicate<A>): Predicate<A>A>(self: Predicate<A>self: interface Predicate<in A>A function that decides whether a value of type A satisfies a condition.
When to use
Use when you want a reusable boolean check for A, especially when you plan
to combine checks with
and
/
or
or pass a predicate to arrays
and iterables.
Details
A predicate returns true or false and never throws by itself. It does not
narrow types unless you use Refinement.
Example (Defining a predicate)
import { Predicate } from "effect"
const isPositive: Predicate.Predicate<number> = (n) => n > 0
console.log(isPositive(1))
Type-level utilities for working with
Predicate
types.
When to use
Use when you need to extract input types from predicate signatures while
writing generic helpers over predicate types.
Details
These utilities are type-only, create no runtime values, and the namespace is
erased at runtime.
Example (Extracting predicate input)
import { Predicate } from "effect"
type IsString = Predicate.Predicate<string>
type Input = Predicate.Predicate.In<IsString>
Predicate<function (type parameter) A in not<A>(self: Predicate<A>): Predicate<A>A>): interface Predicate<in A>A function that decides whether a value of type A satisfies a condition.
When to use
Use when you want a reusable boolean check for A, especially when you plan
to combine checks with
and
/
or
or pass a predicate to arrays
and iterables.
Details
A predicate returns true or false and never throws by itself. It does not
narrow types unless you use Refinement.
Example (Defining a predicate)
import { Predicate } from "effect"
const isPositive: Predicate.Predicate<number> = (n) => n > 0
console.log(isPositive(1))
Type-level utilities for working with
Predicate
types.
When to use
Use when you need to extract input types from predicate signatures while
writing generic helpers over predicate types.
Details
These utilities are type-only, create no runtime values, and the namespace is
erased at runtime.
Example (Extracting predicate input)
import { Predicate } from "effect"
type IsString = Predicate.Predicate<string>
type Input = Predicate.Predicate.In<IsString>
Predicate<function (type parameter) A in not<A>(self: Predicate<A>): Predicate<A>A> {
return (a: Aa) => !self: Predicate<A>self(a: Aa)
}