Make a whole number the rational search finds an integer

BREAKING-CHANGES.md

@@ -92,6 +92,18 @@ solver's check that a limit agrees from both sides goes through the same compari
 | `AreEqualNumerically("2 x (-1/4 + ln(x)/2) + 1/x * 2/4 * x^2", "x ln(x)")` | `false` | `true` |
 | `AreEqualNumerically` of `x ln(x)` and its antiderivative's derivative | `false` | `true` |
 
+### A whole number the rational search finds is an integer
+
+**Silent: a wrong type and a wrong comparison.** The search that reads a number as the rational it is near built its
+result without the check that turns a denominator of 1 into an integer. A value just below a whole number came back as
+the `Rational` `1/1` or `3/1`, which is not an `Integer` and is not equal to `1` or `3`
+([#2069](https://github.com/asc-community/AngouriMath/issues/2069)).
+
+| Input | Was (2.6.0) | Now |
+|---|---|---|
+| `(Entity)0.9999999999999999999999999999m` | `Rational 1/1`, and `== 1` is `false` | `Integer 1` |
+| `(Entity)2.9999999999999999999999999999m` | `Rational 3/1` | `Integer 3` |
+
 ### A computed value is a rational only within half the working digits
 
 **Silent: wrong answers.** A number an evaluation produced became the small rational it was near within a fixed

Sources/AngouriMath/Core/Entity/Continuous/Entity.Continuous.Rational.Definition.cs

@@ -215,7 +215,10 @@ public static Rational Create(ERational value)
                         var rat = FindRationalExactly(inv, iterCount - 1, tolerance);
                         if (rat is null)
                             return null;
-                        return new Rational((intPart * sign + sign / rat.ERational).InLowestTerms());
+                        // Through Create, so that a whole number is an Integer: a value just below one is 0 + 1/1, and
+                        // came back as the Rational 1/1, which is not equal to 1.
+                        // https://github.com/asc-community/AngouriMath/issues/2069
+                        return Rational.Create(intPart * sign + sign / rat.ERational);
                     }
                 }
 

Sources/Tests/UnitTests/Core/NumericDowncasting.cs

@@ -270,5 +270,20 @@ [Fact] public void FromRationalTestRealDowncastingEnabledInt()
             );
 
         #endregion
+
+        /// <summary>
+        /// A whole number the rational search finds is an <see cref="Integer"/>: a value just below one came back
+        /// as the Rational 1/1, which is not equal to 1.
+        /// <a href="https://github.com/asc-community/AngouriMath/issues/2069">#2069</a>
+        /// </summary>
+        [Theory]
+        [InlineData("0.9999999999999999999999999999", 1)]
+        [InlineData("2.9999999999999999999999999999", 3)]
+        public void AWholeNumberFromTheRationalSearchIsAnInteger(string written, int whole)
+        {
+            Entity value = decimal.Parse(written, System.Globalization.CultureInfo.InvariantCulture);
+            value.Should().BeOfType<Integer>();
+            value.Should().Be((Entity)whole);
+        }
     }
-}
+}