[BREAKING] Fix #3602 let setDistinct keep the original order

AUTHORS

@@ -281,5 +281,6 @@ Josh Kelley <[email protected]>
 Richard Taylor <[email protected]>
 NilsDietrich <[email protected]>
 anslem chibuike <[email protected]>
+Ayomide Bamigbade <[email protected]>
 
 # Generated by tools/update-authors.js

HISTORY.md

@@ -4,6 +4,7 @@
 
 - Fix: #3578 interpret empty true-expr of conditional as error (#3581).
   Thanks @gwhitney.
+- Fix: #3597 added nullish type definitions (#3601). Thanks @Ayo1984.
 - Docs: fix #3565, update Matrix documentation (#3591). Thanks @orelbn.
 
 # 2025-11-05, 15.1.0

src/function/set/setDistinct.js

@@ -8,6 +8,7 @@ export const createSetDistinct = /* #__PURE__ */ factory(name, dependencies, ({
   /**
    * Collect the distinct elements of a multiset.
    * A multi-dimension array will be converted to a single-dimension array before the operation.
+   * The items of the returned array will be in order of first occurrence.
    *
    * Syntax:
    *
@@ -22,19 +23,19 @@ export const createSetDistinct = /* #__PURE__ */ factory(name, dependencies, ({
    *    setMultiplicity
    *
    * @param {Array | Matrix}    a  A multiset
-   * @return {Array | Matrix}    A set containing the distinc elements of the multiset
+   * @return {Array | Matrix}    A set containing the distinct elements of the multiset
    */
   return typed(name, {
     'Array | Matrix': function (a) {
       let result
       if (subset(size(a), new Index(0)) === 0) { // if empty, return empty
         result = []
       } else {
-        const b = flatten(Array.isArray(a) ? a : a.toArray()).sort(compareNatural)
+        const b = flatten(Array.isArray(a) ? a : a.toArray())
         result = []
         result.push(b[0])
         for (let i = 1; i < b.length; i++) {
-          if (compareNatural(b[i], b[i - 1]) !== 0) {
+          if (!result.some(item => compareNatural(b[i], item) === 0)) {
             result.push(b[i])
           }
         }

test/typescript-tests/testTypes.ts

@@ -14,6 +14,7 @@ import {
   create,
   divideDependencies,
   EvalFunction,
+  evaluate,
   factory,
   formatDependencies,
   Fraction,
@@ -23,6 +24,7 @@ import {
   Help,
   Index,
   IndexNode,
+  isResultSet,
   isSymbolNode,
   LUDecomposition,
   MapLike,
@@ -38,6 +40,7 @@ import {
   MathType,
   Matrix,
   Node,
+  nullishDependencies,
   ObjectNode,
   OperatorNode,
   OperatorNodeFn,
@@ -50,8 +53,6 @@ import {
   SLUDecomposition,
   SymbolNode,
   Unit,
-  evaluate,
-  isResultSet,
   UnitPrefix
 } from 'mathjs'
 
@@ -2647,12 +2648,13 @@ Factory Test
   }
 
   // Create just the functions we need
-  const { fraction, add, divide, format } = create(
+  const { fraction, add, divide, format, nullish } = create(
     {
       fractionDependencies,
       addDependencies,
       divideDependencies,
-      formatDependencies
+      formatDependencies,
+      nullishDependencies
     },
     config
   )
@@ -2667,6 +2669,9 @@ Factory Test
   assert.strictEqual(format(255, { notation: 'bin' }), '0b11111111')
   assert.strictEqual(format(255, { notation: 'hex' }), '0xff')
   assert.strictEqual(format(255, { notation: 'oct' }), '0o377')
+  assert.strictEqual(nullish(null, 42), 42)
+  assert.strictEqual(nullish(undefined, 'foo'), 'foo')
+  assert.strictEqual(nullish(0, 42), 0)
 }
 
 /**

test/unit-tests/function/set/setDistinct.test.js

@@ -9,10 +9,15 @@ describe('setDistinct', function () {
     assert.deepStrictEqual(math.setDistinct([]), [])
   })
 
+  it('should return the elements of a set in insertion order', function () {
+    assert.deepStrictEqual(math.setDistinct([3, 1, 2, 1, 2]), [3, 1, 2])
+    assert.deepStrictEqual(math.setDistinct(['h', 'e', 'l', 'l', 'o']), ['h', 'e', 'l', 'o'])
+  })
+
   it('should return the distinct elements of a multiset', function () {
     assert.deepStrictEqual(math.setDistinct([1, 1, 2, 2]), [1, 2])
     assert.deepStrictEqual(math.setDistinct([1, 2, 1, 2]), [1, 2])
-    assert.deepStrictEqual(math.setDistinct([1, 2, math.complex(3, 3), 2, math.complex(3, 3)]), [math.complex(3, 3), 1, 2])
+    assert.deepStrictEqual(math.setDistinct([1, 2, math.complex(3, 3), 2, math.complex(3, 3)]), [1, 2, math.complex(3, 3)])
   })
 
   it('should return the same type of output as the inputs', function () {

types/index.d.ts

@@ -1889,6 +1889,18 @@ export interface MathJsInstance extends MathJsFactory {
     x: number | BigNumber | bigint | Complex | Unit | MathCollection
   ): boolean | MathCollection
 
+  /**
+   * Nullish coalescing operator (??). Returns the right-hand side operand
+   * when the left-hand side operand is null or undefined, and otherwise
+   * returns the left-hand side operand. For matrices, the function is
+   * evaluated element wise.
+   * @param x First value to check
+   * @param y Fallback value
+   * @returns Returns y when x is null or undefined, otherwise returns x
+   */
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  nullish(x: any, y: any): any
+
   /**
    * Logical or. Test if at least one value is defined with a
    * nonzero/nonempty value. For matrices, the function is evaluated
@@ -4081,6 +4093,7 @@ export const {
   // logical dependencies
   andDependencies,
   notDependencies,
+  nullishDependencies,
   orDependencies,
   xorDependencies,
 
@@ -5988,6 +6001,16 @@ export interface MathJsChain<TValue> {
     >
   ): MathJsChain<boolean | MathCollection>
 
+  /**
+   * Nullish coalescing operator (??). Returns the right-hand side operand
+   * when the left-hand side operand is null or undefined, and otherwise
+   * returns the left-hand side operand. For matrices, the function is
+   * evaluated element wise.
+   * @param y Fallback value
+   */
+  // eslint-disable-next-line @typescript-eslint/no-explicit-any
+  nullish(this: MathJsChain<any>, y: any): MathJsChain<any>
+
   /**
    * Logical or. Test if at least one value is defined with a
    * nonzero/nonempty value. For matrices, the function is evaluated
@@ -7610,6 +7633,7 @@ export const {
   // logical
   and,
   not,
+  nullish,
   or,
   xor,