From f2f10bd02d37a107c1fabd324819d049bf49b6ca Mon Sep 17 00:00:00 2001
From: Piotr Idzik <vil02@o2.pl>
Date: Thu, 7 Mar 2024 22:09:16 +0000
Subject: [PATCH 1/2] fix: hadnle zeros at the endpoints

---
 Maths/BisectionMethod.js           |  9 ++++-----
 Maths/test/BisectionMethod.test.js | 25 +++++++++++++++++++++++++
 2 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/Maths/BisectionMethod.js b/Maths/BisectionMethod.js
index 49b8c8ecc0..4539e6d466 100644
--- a/Maths/BisectionMethod.js
+++ b/Maths/BisectionMethod.js
@@ -23,7 +23,7 @@ const findRoot = (a, b, func, numberOfIterations) => {
 
   // Bolzano theorem
   const hasRoot = (a, b, func) => {
-    return func(a) * func(b) < 0
+    return func(a) * func(b) <= 0
   }
   if (hasRoot(a, b, func) === false) {
     throw Error(
@@ -45,10 +45,9 @@ const findRoot = (a, b, func, numberOfIterations) => {
   const prod2 = fm * func(b)
 
   // Depending on the sign of the products above, decide which position will m fill (a's or b's)
-  if (prod1 > 0 && prod2 < 0) return findRoot(m, b, func, --numberOfIterations)
-  else if (prod1 < 0 && prod2 > 0)
-    return findRoot(a, m, func, --numberOfIterations)
-  else throw Error('Unexpected behavior')
+  if (prod2 <= 0) return findRoot(m, b, func, --numberOfIterations)
+
+  return findRoot(a, m, func, --numberOfIterations)
 }
 
 export { findRoot }
diff --git a/Maths/test/BisectionMethod.test.js b/Maths/test/BisectionMethod.test.js
index ad865b6ad6..764b36047e 100644
--- a/Maths/test/BisectionMethod.test.js
+++ b/Maths/test/BisectionMethod.test.js
@@ -35,3 +35,28 @@ test('Equation f(x) = sqrt(x) + e^(2*x) - 8*x = 0, has root x = 0.93945851 in [a
   )
   expect(Number(Number(root).toPrecision(8))).toBe(0.93945851)
 })
+
+test('Equation f(x) = x^3 = 0, has root x = 0.0 in [a, b] = [-1.0, 1.0]', () => {
+  const root = findRoot(
+    -1.0,
+    1.0,
+    (x) => {
+      return Math.pow(x, 3)
+    },
+    32
+  )
+  expect(root).toBeCloseTo(0.0, 5)
+})
+
+test('Throws an error when function does not change sign', () => {
+  expect(() =>
+    findRoot(
+      -1.0,
+      1.0,
+      (x) => {
+        return Math.pow(x, 2)
+      },
+      10
+    )
+  ).toThrowError()
+})

From c7cda09fe0f88c84dc7f84688f7427f263852ab0 Mon Sep 17 00:00:00 2001
From: Piotr Idzik <vil02@o2.pl>
Date: Tue, 26 Mar 2024 22:02:21 +0000
Subject: [PATCH 2/2] style: use simpler syntax express polynomials

Co-authored-by: appgurueu <34514239+appgurueu@users.noreply.github.com>
---
 Maths/test/BisectionMethod.test.js | 29 +++--------------------------
 1 file changed, 3 insertions(+), 26 deletions(-)

diff --git a/Maths/test/BisectionMethod.test.js b/Maths/test/BisectionMethod.test.js
index 764b36047e..4a49e8f6a4 100644
--- a/Maths/test/BisectionMethod.test.js
+++ b/Maths/test/BisectionMethod.test.js
@@ -1,14 +1,7 @@
 import { findRoot } from '../BisectionMethod'
 
 test('Equation f(x) = x^2 - 3*x + 2 = 0, has root x = 1 in [a, b] = [0, 1.5]', () => {
-  const root = findRoot(
-    0,
-    1.5,
-    (x) => {
-      return Math.pow(x, 2) - 3 * x + 2
-    },
-    8
-  )
+  const root = findRoot(0, 1.5, (x) => x ** 2 - 3 * x + 2, 8)
   expect(root).toBe(0.9990234375)
 })
 
@@ -37,26 +30,10 @@ test('Equation f(x) = sqrt(x) + e^(2*x) - 8*x = 0, has root x = 0.93945851 in [a
 })
 
 test('Equation f(x) = x^3 = 0, has root x = 0.0 in [a, b] = [-1.0, 1.0]', () => {
-  const root = findRoot(
-    -1.0,
-    1.0,
-    (x) => {
-      return Math.pow(x, 3)
-    },
-    32
-  )
+  const root = findRoot(-1.0, 1.0, (x) => x ** 3, 32)
   expect(root).toBeCloseTo(0.0, 5)
 })
 
 test('Throws an error when function does not change sign', () => {
-  expect(() =>
-    findRoot(
-      -1.0,
-      1.0,
-      (x) => {
-        return Math.pow(x, 2)
-      },
-      10
-    )
-  ).toThrowError()
+  expect(() => findRoot(-1.0, 1.0, (x) => x ** 2, 10)).toThrowError()
 })