Implement clamp_magnitude method for primtives floats & signed integers

Added feature gate, documentation and tests also.

Author: IntegralPilot

compiler/rustc_feature/src/unstable.rs

@@ -434,6 +434,8 @@ declare_features! (
     (unstable, cfg_version, "1.45.0", Some(64796)),
     /// Allows to use the `#[cfi_encoding = ""]` attribute.
     (unstable, cfi_encoding, "1.71.0", Some(89653)),
+    /// Allows using the `clamp_magnitude` method on float and signed integer primitives
+    (unstable, clamp_magnitude, "CURRENT_RUSTC_VERSION", Some(148519)),
     /// Allows `for<...>` on closures and coroutines.
     (unstable, closure_lifetime_binder, "1.64.0", Some(97362)),
     /// Allows `#[track_caller]` on closures and coroutines.

compiler/rustc_span/src/symbol.rs

@@ -661,6 +661,7 @@ symbols! {
         char_to_digit,
         child_id,
         child_kill,
+        clamp_magnitude,
         client,
         clippy,
         clobber_abi,

library/core/src/num/f128.rs

@@ -1276,6 +1276,38 @@ impl f128 {
         self
     }
 
+    /// Clamps this number to a symmetric range centered around zero.
+    ///
+    /// The method clamps the number's magnitude (absolute value) to be at most `limit`.
+    ///
+    /// This is functionally equivalent to `self.clamp(-limit, limit)`, but is more
+    /// explicit about the intent.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `limit` is negative or NaN, as this indicates a logic error.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(f128)]
+    /// #![feature(clamp_magnitude)]
+    /// # #[cfg(all(target_arch = "x86_64", target_os = "linux"))] {
+    /// assert_eq!(5.0f128.clamp_magnitude(3.0), 3.0);
+    /// assert_eq!((-5.0f128).clamp_magnitude(3.0), -3.0);
+    /// assert_eq!(2.0f128.clamp_magnitude(3.0), 2.0);
+    /// assert_eq!((-2.0f128).clamp_magnitude(3.0), -2.0);
+    /// # }
+    /// ```
+    #[inline]
+    #[unstable(feature = "clamp_magnitude", issue = "148519")]
+    #[must_use = "this returns the clamped value and does not modify the original"]
+    pub fn clamp_magnitude(self, limit: f128) -> f128 {
+        assert!(limit >= 0.0, "limit must be non-negative");
+        let limit = limit.abs(); // Canonicalises -0.0 to 0.0
+        self.clamp(-limit, limit)
+    }
+
     /// Computes the absolute value of `self`.
     ///
     /// This function always returns the precise result.

library/core/src/num/f16.rs

@@ -1254,6 +1254,38 @@ impl f16 {
         self
     }
 
+    /// Clamps this number to a symmetric range centered around zero.
+    ///
+    /// The method clamps the number's magnitude (absolute value) to be at most `limit`.
+    ///
+    /// This is functionally equivalent to `self.clamp(-limit, limit)`, but is more
+    /// explicit about the intent.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `limit` is negative or NaN, as this indicates a logic error.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(f16)]
+    /// #![feature(clamp_magnitude)]
+    /// # #[cfg(all(target_arch = "x86_64", target_os = "linux"))] {
+    /// assert_eq!(5.0f16.clamp_magnitude(3.0), 3.0);
+    /// assert_eq!((-5.0f16).clamp_magnitude(3.0), -3.0);
+    /// assert_eq!(2.0f16.clamp_magnitude(3.0), 2.0);
+    /// assert_eq!((-2.0f16).clamp_magnitude(3.0), -2.0);
+    /// # }
+    /// ```
+    #[inline]
+    #[unstable(feature = "clamp_magnitude", issue = "148519")]
+    #[must_use = "this returns the clamped value and does not modify the original"]
+    pub fn clamp_magnitude(self, limit: f16) -> f16 {
+        assert!(limit >= 0.0, "limit must be non-negative");
+        let limit = limit.abs(); // Canonicalises -0.0 to 0.0
+        self.clamp(-limit, limit)
+    }
+
     /// Computes the absolute value of `self`.
     ///
     /// This function always returns the precise result.

library/core/src/num/f32.rs

@@ -1431,6 +1431,35 @@ impl f32 {
         self
     }
 
+    /// Clamps this number to a symmetric range centered around zero.
+    ///
+    /// The method clamps the number's magnitude (absolute value) to be at most `limit`.
+    ///
+    /// This is functionally equivalent to `self.clamp(-limit, limit)`, but is more
+    /// explicit about the intent.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `limit` is negative or NaN, as this indicates a logic error.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(clamp_magnitude)]
+    /// assert_eq!(5.0f32.clamp_magnitude(3.0), 3.0);
+    /// assert_eq!((-5.0f32).clamp_magnitude(3.0), -3.0);
+    /// assert_eq!(2.0f32.clamp_magnitude(3.0), 2.0);
+    /// assert_eq!((-2.0f32).clamp_magnitude(3.0), -2.0);
+    /// ```
+    #[must_use = "this returns the clamped value and does not modify the original"]
+    #[unstable(feature = "clamp_magnitude", issue = "148519")]
+    #[inline]
+    pub fn clamp_magnitude(self, limit: f32) -> f32 {
+        assert!(limit >= 0.0, "limit must be non-negative");
+        let limit = limit.abs(); // Canonicalises -0.0 to 0.0
+        self.clamp(-limit, limit)
+    }
+
     /// Computes the absolute value of `self`.
     ///
     /// This function always returns the precise result.

library/core/src/num/f64.rs

@@ -1429,6 +1429,35 @@ impl f64 {
         self
     }
 
+    /// Clamps this number to a symmetric range centered around zero.
+    ///
+    /// The method clamps the number's magnitude (absolute value) to be at most `limit`.
+    ///
+    /// This is functionally equivalent to `self.clamp(-limit, limit)`, but is more
+    /// explicit about the intent.
+    ///
+    /// # Panics
+    ///
+    /// Panics if `limit` is negative or NaN, as this indicates a logic error.
+    ///
+    /// # Examples
+    ///
+    /// ```
+    /// #![feature(clamp_magnitude)]
+    /// assert_eq!(5.0f64.clamp_magnitude(3.0), 3.0);
+    /// assert_eq!((-5.0f64).clamp_magnitude(3.0), -3.0);
+    /// assert_eq!(2.0f64.clamp_magnitude(3.0), 2.0);
+    /// assert_eq!((-2.0f64).clamp_magnitude(3.0), -2.0);
+    /// ```
+    #[must_use = "this returns the clamped value and does not modify the original"]
+    #[unstable(feature = "clamp_magnitude", issue = "148519")]
+    #[inline]
+    pub fn clamp_magnitude(self, limit: f64) -> f64 {
+        assert!(limit >= 0.0, "limit must be non-negative");
+        let limit = limit.abs(); // Canonicalises -0.0 to 0.0
+        self.clamp(-limit, limit)
+    }
+
     /// Computes the absolute value of `self`.
     ///
     /// This function always returns the precise result.

library/core/src/num/int_macros.rs

@@ -3855,5 +3855,33 @@ macro_rules! int_impl {
         pub const fn max_value() -> Self {
             Self::MAX
         }
+
+        /// Clamps this number to a symmetric range centred around zero.
+        ///
+        /// The method clamps the number's magnitude (absolute value) to be at most `limit`.
+        ///
+        /// This is functionally equivalent to `self.clamp(-limit, limit)`, but is more
+        /// explicit about the intent.
+        ///
+        /// # Examples
+        ///
+        /// ```
+        /// #![feature(clamp_magnitude)]
+        #[doc = concat!("assert_eq!(120", stringify!($SelfT), ".clamp_magnitude(100), 100);")]
+        #[doc = concat!("assert_eq!(-120", stringify!($SelfT), ".clamp_magnitude(100), -100);")]
+        #[doc = concat!("assert_eq!(80", stringify!($SelfT), ".clamp_magnitude(100), 80);")]
+        #[doc = concat!("assert_eq!(-80", stringify!($SelfT), ".clamp_magnitude(100), -80);")]
+        /// ```
+        #[must_use = "this returns the clamped value and does not modify the original"]
+        #[unstable(feature = "clamp_magnitude", issue = "148519")]
+        #[inline]
+        pub fn clamp_magnitude(self, limit: $UnsignedT) -> Self {
+            // Use try_into to handle cases where `limit` is larger than `Self::MAX`.
+            let positive_limit = limit.try_into().unwrap_or(Self::MAX);
+            // By capping `positive_limit` at `Self::MAX`, we ensure the range is symmetric.
+            // `-positive_limit` is thus always representable.
+            let negative_limit = -positive_limit;
+            self.clamp(negative_limit, positive_limit)
+        }
     }
 }

library/coretests/tests/lib.rs

@@ -15,6 +15,7 @@
 #![feature(cfg_target_has_reliable_f16_f128)]
 #![feature(char_internals)]
 #![feature(char_max_len)]
+#![feature(clamp_magnitude)]
 #![feature(clone_to_uninit)]
 #![feature(const_cell_traits)]
 #![feature(const_cmp)]