Rollup merge of #156392 - Wilfred:float_ceil_docs, r=Mark-Simulacrum

Improve doc comments for f32::ceil() and f32::floor()

Previously ::floor() included an example showing behaviour for negative values, but ::ceil() did not. Ensure both have examples of the negative case, for both f32 and f64.

Whilst we're here, tweak the wording slightly so it reads better.

Author: GuillaumeGomez

library/std/src/num/f32.rs

@@ -26,7 +26,7 @@ use crate::sys::cmath;
 
 #[cfg(not(test))]
 impl f32 {
-    /// Returns the largest integer less than or equal to `self`.
+    /// Returns the largest integer that is less than or equal to `self`.
     ///
     /// This function always returns the precise result.
     ///
@@ -50,7 +50,7 @@ impl f32 {
         core::f32::math::floor(self)
     }
 
-    /// Returns the smallest integer greater than or equal to `self`.
+    /// Returns the smallest integer that is greater than or equal to `self`.
     ///
     /// This function always returns the precise result.
     ///
@@ -59,9 +59,11 @@ impl f32 {
     /// ```
     /// let f = 3.01_f32;
     /// let g = 4.0_f32;
+    /// let h = -3.01_f32;
     ///
     /// assert_eq!(f.ceil(), 4.0);
     /// assert_eq!(g.ceil(), 4.0);
+    /// assert_eq!(h.ceil(), -3.0);
     /// ```
     #[doc(alias = "ceiling")]
     #[rustc_allow_incoherent_impl]

library/std/src/num/f64.rs

@@ -26,7 +26,7 @@ use crate::sys::cmath;
 
 #[cfg(not(test))]
 impl f64 {
-    /// Returns the largest integer less than or equal to `self`.
+    /// Returns the largest integer that is less than or equal to `self`.
     ///
     /// This function always returns the precise result.
     ///
@@ -50,7 +50,7 @@ impl f64 {
         core::f64::math::floor(self)
     }
 
-    /// Returns the smallest integer greater than or equal to `self`.
+    /// Returns the smallest integer that is greater than or equal to `self`.
     ///
     /// This function always returns the precise result.
     ///
@@ -59,9 +59,11 @@ impl f64 {
     /// ```
     /// let f = 3.01_f64;
     /// let g = 4.0_f64;
+    /// let h = -3.01_f64;
     ///
     /// assert_eq!(f.ceil(), 4.0);
     /// assert_eq!(g.ceil(), 4.0);
+    /// assert_eq!(h.ceil(), -3.0);
     /// ```
     #[doc(alias = "ceiling")]
     #[rustc_allow_incoherent_impl]