Add primitive numeric traits

library/core/src/primitive/float_macros.rs

@@ -0,0 +1,44 @@
+// Note: currently limiting this to what f16/f128 already support (which isn't much).
+// f32/f64 share essentially their whole API which should be added here eventually.
+
+macro_rules! float_decl {
+    () => {
+        /// Returns `true` if this value is NaN.
+        fn is_nan(self) -> bool;
+
+        /// Returns `true` if `self` has a positive sign, including `+0.0`, NaNs with
+        /// positive sign bit and positive infinity. Note that IEEE 754 doesn't assign any
+        /// meaning to the sign bit in case of a NaN, and as Rust doesn't guarantee that
+        /// the bit pattern of NaNs are conserved over arithmetic operations, the result of
+        /// `is_sign_positive` on a NaN might produce an unexpected result in some cases.
+        /// See [explanation of NaN as a special value](f32) for more info.
+        fn is_sign_positive(self) -> bool;
+
+        /// Returns `true` if `self` has a negative sign, including `-0.0`, NaNs with
+        /// negative sign bit and negative infinity. Note that IEEE 754 doesn't assign any
+        /// meaning to the sign bit in case of a NaN, and as Rust doesn't guarantee that
+        /// the bit pattern of NaNs are conserved over arithmetic operations, the result of
+        /// `is_sign_negative` on a NaN might produce an unexpected result in some cases.
+        /// See [explanation of NaN as a special value](f32) for more info.
+        fn is_sign_negative(self) -> bool;
+    };
+}
+
+macro_rules! float_impl {
+    () => {
+        #[inline]
+        fn is_nan(self) -> bool {
+            Self::is_nan(self)
+        }
+
+        #[inline]
+        fn is_sign_positive(self) -> bool {
+            Self::is_sign_positive(self)
+        }
+
+        #[inline]
+        fn is_sign_negative(self) -> bool {
+            Self::is_sign_negative(self)
+        }
+    };
+}