Start and use a standard-like numbers header

1 files changed, 32 insertions, 0 deletions

diff --git a/common/alnumbers.h b/common/alnumbers.h
new file mode 100644
index 00000000..98994b44
--- /dev/null
+++ b/common/alnumbers.h
@@ -0,0 +1,32 @@
+#ifndef COMMON_ALNUMBERS_H
+#define COMMON_ALNUMBERS_H
+
+#include <utility>
+
+namespace al {
+
+namespace numbers {
+
+namespace detail_ {
+    template<typename T>
+    using as_fp = std::enable_if_t<std::is_floating_point<T>::value, T>;
+} // detail_
+
+template<typename T>
+static constexpr auto pi_v = detail_::as_fp<T>(3.141592653589793238462643383279502884L);
+
+template<typename T>
+static constexpr auto inv_pi_v = detail_::as_fp<T>(0.318309886183790671537767526745028724L);
+
+template<typename T>
+static constexpr auto sqrt3_v = detail_::as_fp<T>(1.732050807568877293527446341505872367L);
+
+static constexpr auto pi = pi_v<double>;
+static constexpr auto inv_pi = inv_pi_v<double>;
+static constexpr auto sqrt3 = sqrt3_v<double>;
+
+} // namespace numbers
+
+} // namespace al
+
+#endif /* COMMON_ALNUMBERS_H */