feat: kata/floating-point-comparison (#735)

* docs: kata description

* docs: sync progress

* feat: kata/floating-point-comparison

---------

Co-authored-by: ParanoidUser <5120290+ParanoidUser@users.noreply.github.com>

docs/README.md

@@ -1,7 +1,7 @@
 # Codewars Handbook ☕️🚀
 
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@@ -25,7 +25,7 @@ slug.
 
 | [1 kyu](/kata/1-kyu/index.md) | [2 kyu](/kata/2-kyu/index.md) | [3 kyu](/kata/3-kyu/index.md) | [4 kyu](/kata/4-kyu/index.md) | [5 kyu](/kata/5-kyu/index.md) | [6 kyu](/kata/6-kyu/index.md) | [7 kyu](/kata/7-kyu/index.md) | [8 kyu](/kata/8-kyu/index.md) | [beta](/kata/beta/index.md) | [retired](/kata/retired/index.md) |
 |:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:-----------------------------:|:---------------------------:|:---------------------------------:|
-| 0 | 1 | 2 | 26 | 48 | 440 | 604 | 226 | 56 | 82 |
+| 0 | 1 | 2 | 26 | 48 | 440 | 604 | 227 | 56 | 82 |
 
 **Note:** The source code is written in Java 17 and may use language features that are incompatible
 with Java 8, 11.

kata/8-kyu/floating-point-comparison/README.md

@@ -0,0 +1,36 @@
+# [Floating point comparison](https://www.codewars.com/kata/floating-point-comparison "https://www.codewars.com/kata/5f9f43328a6bff002fa29eb8")
+
+## Introduction
+
+`float`s have limited precision and are unable to exactly represent some values. Rounding errors accumulate with repeated computation, and
+numbers expected to be equal often differ slightly.
+
+As a result, it is common advice to not use an exact equality comparison (`==`) with floats.
+
+```
+>>> a, b, c = 1e-9, 1e-9, 3.33e7
+>>> (a + b) + c == a + (b + c)
+False
+
+>>> 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 + 0.1 == 1.0
+False
+```
+
+The solution is to check if a computed value is close to an expected value, without requiring them to be exactly equal. It seems very easy,
+but many katas test float results the wrong way.
+
+## Task
+
+You have:
+
+- a float value that comes from a computation and may have accumulated errors up to ±0.001
+- a reference value
+
+The function is bugged and sometimes returns wrong results.
+
+Your task is to correct the bug.
+
+## Note
+
+This kata uses fixed tolerance for simplicity reasons, but usually relative tolerance is better. Fixed tolerance is useful for comparisons
+near zero or when the magnitude of the values is known.

kata/8-kyu/floating-point-comparison/main/FloatingPointComparison.java

@@ -0,0 +1,5 @@
+interface FloatingPointComparison {
+  static boolean approxEquals(double a, double b) {
+    return Math.abs(a - b) < .001;
+  }
+}

kata/8-kyu/floating-point-comparison/test/FloatingPointComparisonTest.java

@@ -0,0 +1,29 @@
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.CsvSource;
+
+class FloatingPointComparisonTest {
+  @ParameterizedTest
+  @CsvSource(textBlock = """
+      -156.24037, -156.24038
+      123.2345, 123.234501
+      -1.234, -1.233999
+      98.7655, 98.7654999
+      -75158.25030, -75158.25017
+      """)
+  void sample(double a, double b) {
+    assertTrue(FloatingPointComparison.approxEquals(a, b));
+  }
+
+  @ParameterizedTest
+  @CsvSource(textBlock = """
+      175.9827, 82.25
+      1456.3652, 1456.3641
+      -7.28495, -7.28596
+      """)
+  void notEquals(double a, double b) {
+    assertFalse(FloatingPointComparison.approxEquals(a, b));
+  }
+}

kata/8-kyu/index.md

@@ -89,6 +89,7 @@
 - [Find the smallest integer in the array](find-the-smallest-integer-in-the-array)
 - [FIXME: Replace all dots](fixme-replace-all-dots)
 - [FIXME: Static electrickery](fixme-static-electrickery)
+- [Floating point comparison](floating-point-comparison)
 - [Formatting decimal places #0](formatting-decimal-places-number-0)
 - [Fuel Calculator: Total Cost](fuel-calculator-total-cost)
 - [Function 1 - hello world](function-1-hello-world)