Add islessgreater() term entry for C++ math-functions

content/cpp/concepts/math-functions/terms/islessgreater/islessgreater.md

@@ -0,0 +1,88 @@
+---
+Title: 'islessgreater()'
+Description: 'Determines if a value is less than or greater than another.'
+Subjects:
+  - 'Computer Science'
+Tags:
+  - 'Functions'
+  - 'Arithmetic'
+CatalogContent:
+  - 'learn-c-plus-plus'
+  - 'paths/computer-science'
+---
+
+The **`islessgreater()`** function determines whether a floating-point value is less than or greater than another floating-point value. Unlike the built-in comparison operators (`<` and `>`), this function does not raise `FE_INVALID` exceptions when the arguments are `NaN`.
+
+## Syntax
+
+```pseudo
+islessgreater(x, y)
+```
+
+**Parameters:**
+
+- `x`: A floating-point or integer value to compare.
+- `y`: A floating-point or integer value to compare.
+
+**Return value:**
+
+The function returns `true` if the two values are unequal and one is strictly less than or strictly greater than the other. It returns `false` when the values are equal or when either argument is `NaN`.
+
+> **Note:** This function is particularly useful when working with floating-point values that might be `NaN`, as it provides a "quiet" comparison that won't trigger floating-point exceptions.
+
+## Example
+
+In the example below, the `islessgreater()` function compares two floating-point values:
+
+```cpp
+#include <iostream>
+#include <cmath>
+using namespace std;
+
+int main() {
+  double x = 5.0;
+  double y = 10.0;
+
+  cout << "islessgreater(5.0, 10.0): " << islessgreater(x, y) << "\n";
+  cout << "islessgreater(10.0, 5.0): " << islessgreater(y, x) << "\n";
+  cout << "islessgreater(5.0, 5.0): " << islessgreater(x, x) << "\n";
+
+  return 0;
+}
+```
+
+This produces the following output:
+
+```shell
+islessgreater(5.0, 10.0): 1
+islessgreater(10.0, 5.0): 1
+islessgreater(5.0, 5.0): 0
+```
+
+## Codebyte Example
+
+The example below demonstrates the `islessgreater()` function with different data types and edge cases, including `NaN` values:
+
+```codebyte/cpp
+#include <iostream>
+#include <cmath>
+using namespace std;
+
+int main() {
+  float f1 = 3.14;
+  float f2 = 2.71;
+  double d1 = 100.0;
+  double d2 = 100.0;
+  long double ld1 = 1.5L;
+  long double ld2 = 2.5L;
+
+  // NaN comparison
+  double nan_val = 0.0 / 0.0;
+  double normal_val = 5.0;
+
+  cout << "islessgreater(3.14, 2.71): " << islessgreater(f1, f2) << "\n";
+  cout << "islessgreater(100.0, 100.0): " << islessgreater(d1, d2) << "\n";
+  cout << "islessgreater(1.5L, 2.5L): " << islessgreater(ld1, ld2) << "\n";
+  cout << "islessgreater(NaN, 5.0): " << islessgreater(nan_val, normal_val) << "\n";
+}
+```