@escapace/typelevel

Collection of small TypeScript type utilities for boolean logic, set operations, tuples, objects, and higher-kinded type plumbing.

The list below assumes import type $ from '@escapace/typelevel' and names each utility by its full path from that import.

Assert

• $.Assert.False<T> asserts that T is exactly $.False.
• $.Assert.True<T> asserts that T is exactly $.True.

Is

• $.Is.Any<T> returns $.True when T is any.
• $.Is.Boolean<T> returns $.True when T extends boolean.
• $.Is.Falsy<T> returns $.True for JavaScript falsy types such as '', 0, false, null, undefined, and void, and may return $.False | $.True for wider scalar types.
• $.Is.Never<T> returns $.True when T is never.
• $.Is.Number<T> returns $.True when T extends number.
• $.Is.Primitive<T> returns $.True when T is a number, boolean, string, or symbol.
• $.Is.String<T> returns $.True when T extends string.
• $.Is.Symbol<T> returns $.True when T extends symbol.
• $.Is.Truthy<T> returns the inverse of $.Is.Falsy<T>.
• $.Is.Unknown<T> returns $.True when T is unknown.

To

• $.To.Boolean<T> converts $.False or $.True to false or true.
• $.To.Intersection<U> converts a union U into an intersection.

Boolean algebra

• $.And<A, B> returns $.True when both operands are $.True.
• $.Equivalence<A, B> returns $.True when both operands are equal.
• $.False is the type-level false value 0.
• $.Implication<A, B> models logical implication and returns $.False only when A is $.True and B is $.False.
• $.Not<T> flips $.False to $.True and $.True to $.False.
• $.Or<A, B> returns $.True when either operand is $.True.
• $.True is the type-level true value 1.
• $.Xor<A, B> returns $.True when exactly one operand is $.True.

Set algebra

• $.Complement<A, B> returns the part of the universal set A that is not in subset B.
• $.Contains<A, B> returns $.True when B is a subset of A.
• $.Difference<A, B> returns the members of A that are not in B.
• $.Has<A, B> returns $.True when A and B share at least one member.
• $.Intersection<A, B> returns the members shared by A and B.
• $.SymmetricDifference<A, B> returns the members that appear in exactly one of A or B.
• $.Union<A, B> returns the union of A and B.

Function

• $.Argument<T, N> returns the Nth argument type of function T using the library's one-based indexing scheme, where 0 resolves to never.
• $.Arguments<T> returns the parameter tuple of function T.

List

• $.Append<A, B> adds A to the end of tuple B.
• $.Concat<A, B> concatenates tuples A and B.
• $.Cons<A, B> is an alias of $.Prepend<A, B>.
• $.Drop<N, T> removes the first N elements from tuple T.
• $.First<T, D> is an alias of $.Head<T, D>.
• $.Flatten<T> flattens a tuple of tuples by one level.
• $.Head<T, D> returns the first element of tuple T, or D when T is empty.
• $.Last<T> returns the last element of tuple T.
• $.List<A> is the base readonly list type readonly A[].
• $.Prepend<A, B> adds A to the front of tuple B.
• $.Repeat<T, N> builds a tuple with T repeated N times.
• $.Reverse<L> reverses tuple L.
• $.Tail<L> returns every element of tuple L except the first.
• $.Take<N, T> returns the first N elements of tuple T.
• $.Values<T> returns the union of the element types in an array-like type T.
• $.Zip<A, B> pairs tuples A and B element by element until either tuple runs out.

Object

• $.Assign<T, U> merges object types and lets keys from U overwrite keys from T.
• $.Omit<T, K> removes keys K from T, distributing across unions.
• $.Prettify<T> remaps T to a plain object shape that is easier to inspect in editor tooltips.
• $.Properties<T, K, F> returns the value type for key K in T, or F for missing keys.

Type and higher-kinded type helpers

• $.Cast<T, P> keeps T when it already extends P; otherwise it falls back to P.
• $.Constructable<T> describes a constructor that produces T.
• $.Equal<A, B> returns $.True when A and B are strictly equal types.
• $.Extends<V, T> returns $.True when V extends T.
• $.HKT<URI, A> is the base interface for unary higher-kinded types.
• $.HKT2<URI, L, A> is the base interface for binary higher-kinded types.
• $.HKT3<URI, U, L, A> is the base interface for ternary higher-kinded types.
• $.HKT4<URI, X, U, L, A> is the base interface for quaternary higher-kinded types.
• $.If<T, Then, Else> selects Then for $.True and Else for $.False.
• $.NoInfer<T> preserves T while reducing inference from that position.
• $.Phantom is the unique symbol used as the placeholder key in the higher-kinded type registries.
• $.Type<URI, A> applies a registered unary higher-kinded type to A.
• $.Type2<URI, L, A> applies a registered binary higher-kinded type to L and A.
• $.Type3<URI, U, L, A> applies a registered ternary higher-kinded type to U, L, and A.
• $.Type4<URI, X, U, L, A> applies a registered quaternary higher-kinded type to X, U, L, and A.
• $.URI2HKT<A> is the augmentation point for unary higher-kinded type mappings.
• $.URI2HKT2<A, B> is the augmentation point for binary higher-kinded type mappings.
• $.URI2HKT3<A, B, C> is the augmentation point for ternary higher-kinded type mappings.
• $.URI2HKT4<A, B, C, D> is the augmentation point for quaternary higher-kinded type mappings.
• $.URIS is the union of registered unary higher-kinded type identifiers.
• $.URIS2 is the union of registered binary higher-kinded type identifiers.
• $.URIS3 is the union of registered ternary higher-kinded type identifiers.
• $.URIS4 is the union of registered quaternary higher-kinded type identifiers.
• $.Widen<T> widens boolean, number, and string literals to their scalar parent types.