From a28bae0d47aa89a17e44e2e4ef75ee239d733c35 Mon Sep 17 00:00:00 2001
From: mb <mb@base10.at>
Date: Sat, 21 Oct 2023 11:05:10 +0200
Subject: [PATCH] add array/stride

---
 docs/src/config-menu.ts                    |  4 +++
 docs/src/pages/en/array/operator/stride.md | 37 ++++++++++++++++++++++
 spec/core/array.spec.ts                    |  2 +-
 spec/core/array.timing.ts                  | 18 ++++++++++-
 spec/core/array/operator/stride.spec.ts    | 31 ++++++++++++++++++
 src/array/operator/index.ts                |  2 ++
 src/array/operator/stride.ts               |  7 ++++
 7 files changed, 99 insertions(+), 2 deletions(-)
 create mode 100644 docs/src/pages/en/array/operator/stride.md
 create mode 100644 spec/core/array/operator/stride.spec.ts
 create mode 100644 src/array/operator/stride.ts

diff --git a/docs/src/config-menu.ts b/docs/src/config-menu.ts
index bec0b20..0718f86 100644
--- a/docs/src/config-menu.ts
+++ b/docs/src/config-menu.ts
@@ -142,6 +142,10 @@ export default {
         "text": "splitInto",
         "link": "en/array/operator/splitInto"
       },
+      {
+        "text": "stride",
+        "link": "en/array/operator/stride"
+      },
       {
         "text": "tail",
         "link": "en/array/operator/tail"
diff --git a/docs/src/pages/en/array/operator/stride.md b/docs/src/pages/en/array/operator/stride.md
new file mode 100644
index 0000000..1ea8ba8
--- /dev/null
+++ b/docs/src/pages/en/array/operator/stride.md
@@ -0,0 +1,37 @@
+---
+title: stride
+description: stride
+layout: ../../../../layouts/MainLayout.astro
+---
+Creates a new array by taking every nth element from the input array.
+
+## Type
+
+```ts
+type stride = (step: number) => <E>(array: E[]) => E[] 
+```
+
+
+## Parameters
+
+- `step` (number): The step size for selecting elements from the input array.
+- `array` (Array): An array of elements from which to select elements.
+
+## Returns
+
+- (Array): A new array containing every nth element from the input array.
+
+## Example
+
+```ts
+import {stride} from 'fnxt/array';
+
+const array = [1, 2, 3, 4, 5, 6, 7];
+const stride = stride(3);
+stride(array) // -> [1, 4, 7]
+```
+
+## See Also
+
+- [skip](./skip)
+- [take](./take)
diff --git a/spec/core/array.spec.ts b/spec/core/array.spec.ts
index 23b6458..58bf824 100644
--- a/spec/core/array.spec.ts
+++ b/spec/core/array.spec.ts
@@ -32,7 +32,7 @@ describe('array', () => {
       'sortByDescending', 'sortDescending', 'sortInPlace',
       'sortInPlace', 'sortInPlaceBy', 'sortInPlaceWith',
       'sortInPlaceWith', 'sortWith', 'sortWith',
-      'splitAt', 'splitInto', 'sum',
+      'splitAt', 'splitInto', 'stride', 'sum',
       'sumBy', 'remove', 'tail', 'take',
       'takeWhile', 'takeWhileInclusive', 'transpose',
       'truncate', 'tryFind', 'tryFindBack',
diff --git a/spec/core/array.timing.ts b/spec/core/array.timing.ts
index cb7b9d8..6cac76e 100644
--- a/spec/core/array.timing.ts
+++ b/spec/core/array.timing.ts
@@ -210,6 +210,21 @@ describe('performance test', function () {
 
     }).timeout(oneMinute);
   });
+  describe('stride', () => {
+    it('stride', () => {
+      const stride = <T>(step: number) => <T>(array: T[]): T[] =>
+        array.filter((_, i) => i % step == 0);
+
+      const data = ARRAY.range(0, length);
+
+      const step = 13;
+      const fnxt = ARRAY.stride(step);
+      const alternative = stride(step);
+
+      run(fnxt, alternative, data);
+
+    }).timeout(oneMinute);
+  });
 
   it('skipWhile', () => {
     const skipWhile = <T>(predicate: Predicate<T>) => (array: T[]): T[] => {
@@ -415,5 +430,6 @@ describe('performance test', function () {
   }).timeout(oneMinute);
 
 
-});
+})
+;
 
diff --git a/spec/core/array/operator/stride.spec.ts b/spec/core/array/operator/stride.spec.ts
new file mode 100644
index 0000000..808e60b
--- /dev/null
+++ b/spec/core/array/operator/stride.spec.ts
@@ -0,0 +1,31 @@
+import {expect} from 'chai';
+import {checkThrow} from '../../../support/checkThrow';
+import {stride} from '../../../../src/array';
+
+describe('stride', () => {
+
+  it('should stride 1', () => {
+    const fn = stride(1);
+    expect(fn([1, 2, 3, 4, 5, 6])).to.eql([1, 2, 3, 4, 5, 6],);
+  });
+
+  it('should stride 2', () => {
+    const fn = stride(2);
+    expect(fn([1, 2, 3, 4, 5, 6])).to.eql([1, 3, 5],);
+  });
+
+  it('should stride 3', () => {
+    const fn = stride(3);
+    expect(fn([1, 2, 3, 4])).to.eql([1, 4],);
+  });
+
+  it('should stride empty', () => {
+    const fn = stride(2);
+    expect(fn([])).to.eql([]);
+  });
+
+  it('should throw if null or undefined', () => {
+    const fn = stride(1);
+    checkThrow(fn);
+  });
+});
diff --git a/src/array/operator/index.ts b/src/array/operator/index.ts
index 9fa951b..bee7472 100644
--- a/src/array/operator/index.ts
+++ b/src/array/operator/index.ts
@@ -53,6 +53,8 @@ export * from './skipWhile';
 export * from './takeWhile';
 export * from './takeWhileInclusive';
 
+export * from './stride';
+
 export * from './where';
 export * from './exists';
 export * from './some';
diff --git a/src/array/operator/stride.ts b/src/array/operator/stride.ts
new file mode 100644
index 0000000..70025d9
--- /dev/null
+++ b/src/array/operator/stride.ts
@@ -0,0 +1,7 @@
+export const stride = (step: number) => <E>(array: E[]): E[] => {
+  const result = [];
+  for (let i = 0; i < array.length; i += step) {
+    result.push(array[i]);
+  }
+  return result;
+};