Added the option to add quadmath functions to namespace std:: (disabled by default since it is Undefined Behaviour)

Author: ZERICO2005

README.md

@@ -3,3 +3,12 @@
 `quadmath_cpp` also includes functions not present in `<quadmath.h>`, such as `islessgreater(x, y)` and `fpclassify(x)` from C++11, in addition to a few C23 functions like `iseqsig(x, y)`.
 
 Include the `quadmath_cpp.h` header in your code to use it. The header should compile fine on GCC from C++98 to C++23
+
+***
+
+If you want to bring `quadmath_cpp` into the `std::` namespace, define `QUADMATH_CPP_NAMESPACE_STD` to non-zero before including the header.
+```c++
+#define QUADMATH_CPP_NAMESPACE_STD 1
+#include "quadmath_cpp.h"
+```
+This will allow you to call `std::sin(x)` and `std::pow(x, y)`. However, extending the `std::` namespace is undefined behaviour, so take caution with this feature.

quadmath_cpp.h

@@ -1,9 +1,9 @@
 /*
-**	Author: zerico2005 (2024 - 2025)
-**	Project: quadmath_cpp
-**	License: MIT License
-**	A copy of the MIT License should be included with
-**	this project. If not, see https://opensource.org/license/MIT
+** Author: zerico2005 (2024 - 2025)
+** Project: quadmath_cpp
+** License: MIT License
+** A copy of the MIT License should be included with
+** this project. If not, see https://opensource.org/license/MIT
 */
 
 #ifndef QUADMATH_CPP_H
@@ -13,13 +13,22 @@
 // <quadmath.h> overloads
 //------------------------------------------------------------------------------
 
+#ifndef QUADMATH_CPP_NAMESPACE_STD
+/* disabled by default */
+#define QUADMATH_CPP_NAMESPACE_STD 0
+#endif
+
 #include <quadmath.h>
 
 #if __cplusplus >= 201103L
 	/* for fpclassify return values */
 	#include <cmath>
 #endif
 
+#if QUADMATH_CPP_NAMESPACE_STD
+namespace std {
+#endif
+
 /* Classification */
 
 inline bool signbit(__float128 x) { return (signbitq(x) != 0); }
@@ -174,4 +183,8 @@ inline __float128 erfc(__float128 x) { return erfcq(x); }
 inline __float128 lgamma(__float128 x) { return lgammaq(x); }
 inline __float128 tgamma(__float128 x) { return tgammaq(x); }
 
+#if QUADMATH_CPP_NAMESPACE_STD
+}
+#endif
+
 #endif /* QUADMATH_CPP_H */

test/src/main.cpp

@@ -1,9 +1,9 @@
 /*
-**	Author: zerico2005 (2024 - 2025)
-**	Project: quadmath_cpp
-**	License: MIT License
-**	A copy of the MIT License should be included with
-**	this project. If not, see https://opensource.org/license/MIT
+** Author: zerico2005 (2024 - 2025)
+** Project: quadmath_cpp
+** License: MIT License
+** A copy of the MIT License should be included with
+** this project. If not, see https://opensource.org/license/MIT
 */
 
 #include <cassert>
@@ -17,6 +17,7 @@
 
 #include <quadmath.h>
 
+#define QUADMATH_CPP_NAMESPACE_STD 0
 #include "../../quadmath_cpp.h"
 
 void basic_test() {