Add doctests for f16 and f128 library functions where possible

Author: tgross35

core/src/num/f128.rs

@@ -228,6 +228,16 @@ impl f128 {
     /// 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.
+    ///
+    /// ```
+    /// #![feature(f128)]
+    ///
+    /// let f = 7.0_f128;
+    /// let g = -7.0_f128;
+    ///
+    /// assert!(f.is_sign_positive());
+    /// assert!(!g.is_sign_positive());
+    /// ```
     #[inline]
     #[must_use]
     #[unstable(feature = "f128", issue = "116909")]
@@ -241,6 +251,16 @@ impl f128 {
     /// 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.
+    ///
+    /// ```
+    /// #![feature(f128)]
+    ///
+    /// let f = 7.0_f128;
+    /// let g = -7.0_f128;
+    ///
+    /// assert!(!f.is_sign_negative());
+    /// assert!(g.is_sign_negative());
+    /// ```
     #[inline]
     #[must_use]
     #[unstable(feature = "f128", issue = "116909")]

core/src/num/f16.rs

@@ -224,6 +224,16 @@ impl f16 {
     /// 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.
+    ///
+    /// ```
+    /// #![feature(f16)]
+    ///
+    /// let f = 7.0_f16;
+    /// let g = -7.0_f16;
+    ///
+    /// assert!(f.is_sign_positive());
+    /// assert!(!g.is_sign_positive());
+    /// ```
     #[inline]
     #[must_use]
     #[unstable(feature = "f16", issue = "116909")]
@@ -237,6 +247,16 @@ impl f16 {
     /// 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.
+    ///
+    /// ```
+    /// #![feature(f16)]
+    ///
+    /// let f = 7.0_f16;
+    /// let g = -7.0_f16;
+    ///
+    /// assert!(!f.is_sign_negative());
+    /// assert!(g.is_sign_negative());
+    /// ```
     #[inline]
     #[must_use]
     #[unstable(feature = "f16", issue = "116909")]

core/src/num/f64.rs

@@ -1111,7 +1111,6 @@ impl f64 {
     /// ```
     /// assert!((1f64).to_bits() != 1f64 as u64); // to_bits() is not casting!
     /// assert_eq!((12.5f64).to_bits(), 0x4029000000000000);
-    ///
     /// ```
     #[must_use = "this returns the result of the operation, \
                   without modifying the original"]