uhd: math: Add a sign() function

We've been having issues with moving locations of Boost headers for this
function, and it's simple enough to implement ourselves.

2 files changed, 22 insertions, 0 deletions

diff --git a/host/include/uhd/utils/math.hpp b/host/include/uhd/utils/math.hpp
index becc256f1..4918ddf2e 100644
--- a/host/include/uhd/utils/math.hpp
+++ b/host/include/uhd/utils/math.hpp
@@ -263,6 +263,21 @@ inline IntegerType gcd(IntegerType x, IntegerType y)
     return _bmint::gcd<IntegerType>(x, y);
 }
 
+//! Returns the sign of x
+//
+// Note: This is equivalent to the Boost.Math version, but without the
+// dependency.
+//
+// Returns +1 for positive arguments, -1 for negative arguments, and 0 if x is
+// zero.
+template <typename T>
+inline constexpr int sign(T x)
+{
+    // Note: If T is unsigned, then this will compile with a warning. Should
+    // we need that, expand the template logic.
+    return (T(0) < x) - (x < T(0));
+}
+
 } // namespace math
 } // namespace uhd
 
diff --git a/host/tests/math_test.cpp b/host/tests/math_test.cpp
index c1b6793bb..1fb01f5c1 100644
--- a/host/tests/math_test.cpp
+++ b/host/tests/math_test.cpp
@@ -17,3 +17,10 @@ BOOST_AUTO_TEST_CASE(test_gcd)
 {
     BOOST_CHECK_EQUAL(uhd::math::gcd<int>(6, 15), 3);
 }
+
+BOOST_AUTO_TEST_CASE(test_sign)
+{
+    BOOST_CHECK_EQUAL(uhd::math::sign(2.3), +1);
+    BOOST_CHECK_EQUAL(uhd::math::sign(-2.3), -1);
+    BOOST_CHECK_EQUAL(uhd::math::sign(0.0), 0);
+}