From 5a9440dd17221ded73d11d01241865301eeb0214 Mon Sep 17 00:00:00 2001
From: Myzel394 <50424412+Myzel394@users.noreply.github.com>
Date: Sun, 21 Jul 2024 18:55:12 +0200
Subject: [PATCH] fix(evaluator): Improve sin and cos threshold values

Signed-off-by: Myzel394 <50424412+Myzel394@users.noreply.github.com>
---
 .../sadellie/evaluatto/BigDecimalMath.kt      | 21 +++++++++++++++++--
 .../github/sadellie/evaluatto/Expression.kt   |  7 ++++++-
 2 files changed, 25 insertions(+), 3 deletions(-)

diff --git a/data/evaluatto/src/main/java/io/github/sadellie/evaluatto/BigDecimalMath.kt b/data/evaluatto/src/main/java/io/github/sadellie/evaluatto/BigDecimalMath.kt
index ad35f5cb..cda7b230 100644
--- a/data/evaluatto/src/main/java/io/github/sadellie/evaluatto/BigDecimalMath.kt
+++ b/data/evaluatto/src/main/java/io/github/sadellie/evaluatto/BigDecimalMath.kt
@@ -26,9 +26,19 @@ import kotlin.math.asin
 import kotlin.math.atan
 import kotlin.math.pow
 
+// Dirty hack to avoid -0.000000000001
+val PI_THRESHOLD = BigDecimal("0.000000000000001")
+
 internal fun BigDecimal.sin(radianMode: Boolean): BigDecimal {
     val angle: Double = if (radianMode) this.toDouble() else Math.toRadians(this.toDouble())
-    return kotlin.math.sin(angle).toBigDecimal()
+
+    val result = kotlin.math.sin(angle).toBigDecimal()
+
+    if (result.abs() < PI_THRESHOLD) {
+        return BigDecimal.ZERO
+    }
+
+    return result
 }
 
 internal fun BigDecimal.arsin(radianMode: Boolean): BigDecimal {
@@ -38,7 +48,14 @@ internal fun BigDecimal.arsin(radianMode: Boolean): BigDecimal {
 
 internal fun BigDecimal.cos(radianMode: Boolean): BigDecimal {
     val angle: Double = if (radianMode) this.toDouble() else Math.toRadians(this.toDouble())
-    return kotlin.math.cos(angle).toBigDecimal()
+
+    val result = kotlin.math.cos(angle).toBigDecimal()
+
+    if (result.abs() < PI_THRESHOLD) {
+        return BigDecimal.ZERO
+    }
+
+    return result
 }
 
 internal fun BigDecimal.arcos(radianMode: Boolean): BigDecimal {
diff --git a/data/evaluatto/src/main/java/io/github/sadellie/evaluatto/Expression.kt b/data/evaluatto/src/main/java/io/github/sadellie/evaluatto/Expression.kt
index f0a648ca..39197b5b 100644
--- a/data/evaluatto/src/main/java/io/github/sadellie/evaluatto/Expression.kt
+++ b/data/evaluatto/src/main/java/io/github/sadellie/evaluatto/Expression.kt
@@ -93,6 +93,10 @@ class Expression(
                 }
 
                 moveIfMatched(Token.Operator.divide) -> {
+                    // Adding those `setScale` calls have been added in
+                    // 36a931c7d175b5cad52ff3abceb7784b0bb82aac to fix #18
+                    // I'm not sure if this is the correct way to fix it, but it
+                    // seems to be working
                     val divisor = parseFactor().setScale(MAX_PRECISION)
                     if (divisor.compareTo(BigDecimal.ZERO) == 0) throw ExpressionException.DivideByZero()
 
@@ -166,7 +170,8 @@ class Expression(
 
         // sin
         if (moveIfMatched(Token.Func.sin)) {
-            expr = parseFuncParentheses().sin(radianMode)
+            val x = parseFuncParentheses()
+            expr = x.sin(radianMode)
         }
 
         // cos