Add additional object utilities + natural number reifications + Iso module.

changelog.md

@@ -1,5 +1,26 @@
 # Changelog
 
+## [0.26.0]
+
+- Introduce the `Iso` module for isomorphic bijections.
+  - Add `Iso.String.Chars` to wrap the process of iterating over chars.
+  - Add `Iso.String.Words` to wrap the process of iterating over words.
+  - Add `Iso.NaturalNumber.Increment` to wrap the process of incrementing a number.
+  - Add `Iso.NaturalNumber.Decrement` to wrap the process of decrementing a number.
+  - Add `Iso.NaturalNumber.Digits` to wrap the process of converting a natural number to a list of digits.
+- Add `Object.DeepEntries` to get all deep paths and values in an object.
+- Add `Object.FromEntries` to create an object from a list of key-value pairs.
+- Add `Object.IsObject` to check if a value is an object.
+- Reify `NaturalNumber.DivideBy` to a value-level function.
+- Reify `NaturalNumber.Divide` to a value-level function.
+- Reify `NaturalNumber.IsEven` to a value-level function.
+- Reify `NaturalNumber.IsOdd` to a value-level function.
+- Add `NaturalNumber.Undigits` to convert a list of digits to a natural number.
+- Reify `String.First` and `String.Last` to value-level functions.
+- Reify `String.Init` and `String.Tail` to value-level functions.
+- Add `String.Unwords` to join a list of strings with a space delimiter.
+- Add `String.RepeatBy` to repeat a string by a given number (argument swapped).
+
 ## [0.25.2]
 
 - Fix `List.Sort` to work with 2-ary comparators.

pkg/package.json

@@ -1,6 +1,6 @@
 {
   "name": "hkt-toolbelt",
-  "version": "0.25.2",
+  "version": "0.26.0",
   "description": "Functional and composable type utilities",
   "types": "./index.d.ts",
   "main": "./index.js",

src/index.ts

@@ -6,6 +6,7 @@ export * as Digit from './digit'
 export * as DigitList from './digit-list'
 export * as Function from './function'
 export * as Integer from './integer'
+export * as Iso from './iso'
 export * as Kind from './kind'
 export * as List from './list'
 export * as Loop from './loop'
@@ -29,6 +30,7 @@ import * as Digit from './digit'
 import * as DigitList from './digit-list'
 import * as Function from './function'
 import * as Integer from './integer'
+import * as Iso from './iso'
 import * as Kind from './kind'
 import * as List from './list'
 import * as Loop from './loop'
@@ -53,6 +55,7 @@ const _ = {
   Digit,
   Function,
   Integer,
+  Iso,
   Kind,
   List,
   Loop,

src/iso.ts

@@ -0,0 +1,24 @@
+export * from './iso/'
+
+/**
+ * The `Iso` module contains various isomorphisms. These isomorphisms are used
+ * to transform between different representations of the same type.
+ *
+ * Generally, isomorphisms consist of a mapping and an inverse mapping.
+ * The isomorphism takes in a kind, and returns a new kind where the input is
+ * transformed via the primary mapping, and the output is transformed via the
+ * inverse mapping.
+ *
+ * A very common operation is to perform a .split(""), do some operations, and
+ * then .join("") the result. This can be combined into a single step using
+ * the `Iso` module.
+ *
+ * @example
+ * ```ts
+ * import { String, Iso } from "hkt-toolbelt";
+ *
+ * type T0 = $<Iso.String.Words, $<List.Map, String.Capitalize>>;
+ * type T1 = $<T0, 'foo bar baz'>; // 'Foo Bar Baz'
+ * ```
+ */
+declare module './iso' {}

src/iso/index.ts

@@ -0,0 +1,14 @@
+export * as NaturalNumber from './natural-number'
+export * as String from './string'
+
+import * as NaturalNumber from './natural-number'
+import * as String from './string'
+
+const _ = {
+  NaturalNumber: NaturalNumber,
+  String: String
+}
+
+type _ = typeof _
+
+export default _

src/iso/natural-number.ts

@@ -0,0 +1,16 @@
+export * from './natural-number/'
+
+/**
+ * The `Iso.NaturalNumber` module contains various number-related isomorphisms.
+ * These first compute some transformation on the input, and then apply the
+ * inverse transformation to the output.
+ *
+ * @example
+ * ```ts
+ * import { Iso } from "hkt-toolbelt";
+ *
+ * type T0 = $<Iso.NaturalNumber.Increment, $<NaturalNumber.Multiply, 2>>;
+ * type T1 = $<T0, 10>; // (N + 1) * 2 - 1 = 21
+ * ```
+ */
+declare module './natural-number' {}

src/iso/natural-number/decrement.test.ts

@@ -0,0 +1,15 @@
+import { $, Iso, NaturalNumber, Test } from '../..'
+
+type Decrement_Spec = [
+  /**
+   * Can wrap a kind i.e. f(n - 1) + 1, for f(x) = x * 2
+   */
+  Test.Expect<
+    $<$<Iso.NaturalNumber.Decrement, $<NaturalNumber.Multiply, 2>>, 10>,
+    19
+  >
+]
+
+it('should wrap a kind i.e. f(n - 1) + 1, for f(x) = x * 2', () => {
+  expect(Iso.NaturalNumber.decrement(NaturalNumber.multiply(2))(10)).toBe(19)
+})

src/iso/natural-number/decrement.ts

@@ -0,0 +1,58 @@
+import { $, Type, Kind, NaturalNumber } from '../..'
+
+/**
+ * Given a kind, return an isomorphism such that the input is decremented by
+ * one, and the output is incremented by one.
+ *
+ * @param {Kind.Kind} K - The kind to wrap with an increment/decrement.
+ *
+ * @example
+ * ```ts
+ * import { Iso } from "hkt-toolbelt";
+ *
+ * type T0 = Iso.NaturalNumber._$decrement<$<NaturalNumber.Multiply, 2>>;
+ * type T1 = $<T0, 10>; // (N - 1) * 2 + 1 = 19
+ * ```
+ */
+export type _$decrement<K extends Kind.Kind> = $<
+  Kind.Pipe,
+  [NaturalNumber.Decrement, K, NaturalNumber.Increment]
+>
+
+/**
+ * Given a kind, return an isomorphism such that the input is decremented by
+ * one, and the output is incremented by one.
+ *
+ * @param {Kind.Kind} K - The kind to wrap with an increment/decrement.
+ *
+ * @example
+ * ```ts
+ * import { Iso } from "hkt-toolbelt";
+ *
+ * type T0 = $<Iso.NaturalNumber.Decrement, $<NaturalNumber.Multiply, 2>>;
+ * type T1 = $<T0, 10>; // (N - 1) * 2 + 1 = 19
+ * ```
+ */
+export interface Decrement extends Kind.Kind {
+  f(x: Type._$cast<this[Kind._], Kind.Kind>): _$decrement<typeof x>
+}
+
+/**
+ * Given a kind, return an isomorphism such that the input is decremented by
+ * one, and the output is incremented by one.
+ *
+ * @param {Kind.Kind} K - The kind to wrap with an increment/decrement.
+ *
+ * @example
+ * ```ts
+ * import { Iso } from "hkt-toolbelt";
+ *
+ * const T0 = Iso.NaturalNumber.decrement(NaturalNumber.multiply(2));
+ * const T1 = T0(10); // (N - 1) * 2 + 1 = 19
+ * ```
+ */
+export const decrement = ((f: Kind._$reify<Kind.Kind<(x: number) => number>>) =>
+  (x: number) =>
+    NaturalNumber.increment(
+      f(NaturalNumber.decrement(x))
+    )) as Kind._$reify<Decrement>

src/iso/natural-number/digits.test.ts

@@ -0,0 +1,22 @@
+import { $, Iso, NaturalNumber, Test, List } from '../..'
+
+type Digits_Spec = [
+  /**
+   * Can convert a natural number to a list of digits.
+   */
+  Test.Expect<
+    $<
+      $<Iso.NaturalNumber.Digits, $<List.Map, $<NaturalNumber.Multiply, 2>>>,
+      99
+    >,
+    1818
+  >
+]
+
+it('should convert a natural number to a list of digits', () => {
+  const result = Iso.NaturalNumber.digits(List.map(NaturalNumber.multiply(2)))(
+    99
+  )
+
+  expect(result).toBe(1818)
+})

src/iso/natural-number/digits.ts

@@ -0,0 +1,65 @@
+import { $, Type, Kind, NaturalNumber, Number } from '../..'
+
+/**
+ * Given a kind, return an isomorphism such that the input is converted to a
+ * list of digits, and the output is converted from a list of digits back to a
+ * natural number.
+ *
+ * @param {Kind.Kind} K - The kind to convert to a natural number.
+ *
+ * @example
+ * ```ts
+ * import { Iso } from "hkt-toolbelt";
+ *
+ * type T0 = Iso.NaturalNumber._$digits<$<List.Map<$<NaturalNumber.Multiply, 2>>>;
+ * type T1 = $<T0, 99>; // 1818
+ * ```
+ */
+export type _$digits<
+  K extends Kind.Kind<(x: Number.Number[]) => Number.Number[]>
+> = $<Kind.Pipe, [NaturalNumber.Digits, K, NaturalNumber.Undigits]>
+
+/**
+ * Given a kind, return an isomorphism such that the input is converted to a
+ * list of digits, and the output is converted from a list of digits back to a
+ * natural number.
+ *
+ * @param {Kind.Kind} K - The kind to convert to a natural number.
+ *
+ * @example
+ * ```ts
+ * import { Iso } from "hkt-toolbelt";
+ *
+ * type T0 = $<Iso.NaturalNumber.Digits, $<List.Map, $<NaturalNumber.Multiply, 2>>>
+ * type T1 = $<T0, 99>; // 1818
+ * ```
+ */
+export interface Digits extends Kind.Kind {
+  f(
+    x: Type._$cast<
+      this[Kind._],
+      Kind.Kind<(x: Number.Number[]) => Number.Number[]>
+    >
+  ): _$digits<typeof x>
+}
+
+/**
+ * Given a kind, return an isomorphism such that the input is converted to a
+ * list of digits, and the output is converted from a list of digits back to a
+ * natural number.
+ *
+ * @param {Kind.Kind} K - The kind to convert to a natural number.
+ *
+ * @example
+ * ```ts
+ * import { Iso } from "hkt-toolbelt";
+ *
+ * const T0 = Iso.NaturalNumber.digits(List.map(NaturalNumber.multiply(2)));
+ * const T1 = T0(99); // 1818
+ * ```
+ */
+export const digits = ((
+    f: Kind._$reify<Kind.Kind<(x: Number.Number[]) => number[]>>
+  ) =>
+  (x: number) =>
+    NaturalNumber.undigits(f(NaturalNumber.digits(x)))) as Kind._$reify<Digits>

src/iso/natural-number/increment.test.ts

@@ -0,0 +1,15 @@
+import { $, Iso, NaturalNumber, Test } from '../..'
+
+type Increment_Spec = [
+  /**
+   * Can wrap a kind i.e. f(n + 1) - 1, for f(x) = x * 2
+   */
+  Test.Expect<
+    $<$<Iso.NaturalNumber.Increment, $<NaturalNumber.Multiply, 2>>, 10>,
+    21
+  >
+]
+
+it('should wrap a kind i.e. f(n + 1) - 1, for f(x) = x * 2', () => {
+  expect(Iso.NaturalNumber.increment(NaturalNumber.multiply(2))(10)).toBe(21)
+})

src/iso/natural-number/increment.ts

@@ -0,0 +1,58 @@
+import { $, Type, Kind, NaturalNumber } from '../..'
+
+/**
+ * Given a kind, return an isomorphism such that the input is incremented by
+ * one, and the output is decremented by one.
+ *
+ * @param {Kind.Kind} K - The kind to wrap with an increment/decrement.
+ *
+ * @example
+ * ```ts
+ * import { Iso } from "hkt-toolbelt";
+ *
+ * type T0 = Iso.NaturalNumber._$increment<$<NaturalNumber.Multiply, 2>>;
+ * type T1 = $<T0, 10>; // (N + 1) * 2 - 1 = 21
+ * ```
+ */
+export type _$increment<K extends Kind.Kind> = $<
+  Kind.Pipe,
+  [NaturalNumber.Increment, K, NaturalNumber.Decrement]
+>
+
+/**
+ * Given a kind, return an isomorphism such that the input is incremented by
+ * one, and the output is decremented by one.
+ *
+ * @param {Kind.Kind} K - The kind to wrap with an increment/decrement.
+ *
+ * @example
+ * ```ts
+ * import { Iso } from "hkt-toolbelt";
+ *
+ * type T0 = $<Iso.NaturalNumber.Increment, $<NaturalNumber.Multiply, 2>>;
+ * type T1 = $<T0, 10>; // (N + 1) * 2 - 1 = 21
+ * ```
+ */
+export interface Increment extends Kind.Kind {
+  f(x: Type._$cast<this[Kind._], Kind.Kind>): _$increment<typeof x>
+}
+
+/**
+ * Given a kind, return an isomorphism such that the input is incremented by
+ * one, and the output is decremented by one.
+ *
+ * @param {Kind.Kind} K - The kind to wrap with an increment/decrement.
+ *
+ * @example
+ * ```ts
+ * import { Iso } from "hkt-toolbelt";
+ *
+ * const T0 = Iso.NaturalNumber.increment(NaturalNumber.multiply(2));
+ * const T1 = T0(10); // (N + 1) * 2 - 1 = 21
+ * ```
+ */
+export const increment = ((f: Kind._$reify<Kind.Kind<(x: number) => number>>) =>
+  (x: number) =>
+    NaturalNumber.decrement(
+      f(NaturalNumber.increment(x))
+    )) as Kind._$reify<Increment>

src/iso/natural-number/index.ts

@@ -0,0 +1,3 @@
+export * from './decrement'
+export * from './digits'
+export * from './increment'

src/iso/string.ts

@@ -0,0 +1,16 @@
+export * from './string/'
+
+/**
+ * The `Iso.String` module contains various string-related isomorphisms. These
+ * isomorphisms are used to transform between different representations of
+ * strings.
+ *
+ * @example
+ * ```ts
+ * import { String, Iso } from "hkt-toolbelt";
+ *
+ * type T0 = $<Iso.String.Words, $<List.Map, String.Capitalize>>;
+ * type T1 = $<T0, 'foo bar baz'>; // 'Foo Bar Baz'
+ * ```
+ */
+declare module './string' {}

src/iso/string/chars.test.ts

@@ -0,0 +1,15 @@
+import { $, Iso, String, Test, List } from '../..'
+
+type Chars_Spec = [
+  /**
+   * Can repeat each character of a string by two.
+   */
+  Test.Expect<
+    $<$<Iso.String.Chars, $<List.Map, $<String.RepeatBy, 2>>>, 'bar'>,
+    'bbaarr'
+  >
+]
+
+it('should repeat each character of a string by two', () => {
+  expect(Iso.String.chars(List.map(String.repeatBy(2)))('bar')).toBe('bbaarr')
+})