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@swim/util

v4.0.0

Published

Interfaces for ordering, equality, hashing, type conversions, functional maps, interpolators, scales, iterators, builders, key-value maps, caches, and assertions

Downloads

319

Readme

Swim Swim Util Library

The Swim Util library provides interfaces for ordering, equality, hashing, type conversions, functional maps, interpolators, scales, iterators, builders, key-value maps, caches, and assertions.

Overview

Ordering, equality, and hashing

Swim Util exports Comparable, Equals, and HashCode interfaces that can be implemented by ordered, equatable, and hash-able classes, respectively.

export interface Comparable<T> {
  compareTo(that: T): number;
}
export interface Equals {
  equals(that: unknown): boolean;
}
export interface HashCode extends Equals {
  hashCode(): number;
}

The exported Objects object supports generic comparison, equality testing, and hashing of arbitrary JavaScript values, including primitives, arrays, and objects.

Objects.compare(x: unknown, y: unknown): 0 | 1 | -1 returns the relative sort order of two comparable values. If x implements Comparable, then Objects.compare delegates to x's compareTo method. If x and y are both numbers, or both strings, they are compared lexicographically. If x and y are both arrays, then each corresponding element is compared, in turn, using Objects.compare. If x and y are both objects, then each entry is compared first by key, then by value, using Objects.compare. Values of incompatible types sort in a deterministic order based on type.

Objects.equal(x: unknown, y: unknown): boolean returns true if two values are equivalent. If x implements Equals, then Objects.equal delegates to x's equals method. If x and y are both primitives, then they are compared by value. If x and y are both arrays, then each corresponding element is tested for equality, in turn, using Objects.equal. If x and y are both objects, then each entry is tested for equality furst by key, then by value, using Objects.equal.

Objects.hash(x: unknown): number returns a consistent hash code for x. If x implements HashCode, then Objects.hash delegate's to x's hashCode method. If x is a primitive, it is hashed using the Murmur3 hashing algorithm. If x is an array, each element is hashed individually using Objects.hash, and the hash codes of all elements get mixed together. If x is an object, each entry has its key and value hashed using Objects.hash, and the hash codes of all entries get mixed together.

The exported Murmur3 object implements the 32-bit MurmurHash algorithm, version 3.

Builder interfaces

The exported Builder interface abstracts over construction of collections. And the PairBuilder interface abstracts over construction of key-value maps, and other pair-containing collections.

export interface Builder<I, O> {
  push(...inputs: I[]): void;
  build(): O;
}
export interface PairBuilder<K, V, O> {
  add(key: K, value: V): void;
  build(): O;
}

Map interfaces

Swim Util defines three key-value map interfaces: an ES6-compatible Map interface, as well as an OrderedMap interface, and a ReducedMap interface. An OrderedMap has its entries sorted by key order. A ReducedMap is an OrderedMap that memoizes partial combinations of sub-elements to support efficient, incremental reduction of continuously mutating datasets.

Assertions

The exported Assert interface provides a common API for constraint testing and contract enforcement. The exported assert singleton provides a default Assert implementation that throws AssertException on assert failure.