Implement recip.

Part of #11.
iliekturtles · May 28, 2017 · e0f355c · e0f355c
1 parent ee01efe
commit e0f355c
Show file tree

Hide file tree

Showing 3 changed files with 41 additions and 1 deletion.
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -16,7 +16,7 @@
  * [Breaking] A new feature, `std`, is now available and is enabled by default. `uom` can still be
    compiled with `no_std` by using `--no-default-features` when compiling the crate or
    `default-features = false` in the `dependencies` section of `Cargo.toml`
- * [#11] `cbrt` and `sqrt` are implemented for `Quantity`.
+ * [#11] `cbrt`, `recip`, and `sqrt` are implemented for `Quantity`.
 
 ### Changed
  * [#28](https://github.com/iliekturtles/uom/issues/28) `Quantity` fields made public in order to

diff --git a/src/system.rs b/src/system.rs
@@ -225,6 +225,8 @@ macro_rules! system {
 
         // Type aliases for dimensions where all exponents of the factors are the given value.
         #[cfg(feature = "std")]
+        type DN1 = $quantities<$(replace_ty!($symbol $crate::typenum::N1)),+>;
+        #[cfg(feature = "std")]
         type DP2 = $quantities<$(replace_ty!($symbol $crate::typenum::P2)),+>;
         #[cfg(feature = "std")]
         type DP3 = $quantities<$(replace_ty!($symbol $crate::typenum::P3)),+>;
@@ -463,6 +465,30 @@ macro_rules! system {
                         }
                     }
 
+                    /// Takes the reciprocal (inverse) of a number, `1/x`.
+                    ///
+                    /// ```
+                    #[cfg_attr(feature = "f64", doc = " # use uom::si::f64::*;")]
+                    #[cfg_attr(not(feature = "f64"), doc = " # use uom::si::f32::*;")]
+                    /// # use uom::si::time::second;
+                    /// // TODO #30 implement Frequency.
+                    /// let f/*: Frequency*/ = Time::new::<second>(1.0).recip();
+                    /// ```
+                    #[cfg(feature = "std")]
+                    #[inline(always)]
+                    pub fn recip(self) ->
+                        Quantity<<D as $crate::stdlib::ops::Mul<DN1>>::Output, U, $V>
+                        where D: $crate::stdlib::ops::Mul<DN1>,
+                              U: Units<<D as $crate::stdlib::ops::Mul<DN1>>::Output, $V>,
+                              <D as $crate::stdlib::ops::Mul<DN1>>::Output: Dimension,
+                    {
+                        Quantity {
+                            dimension: $crate::stdlib::marker::PhantomData,
+                            units: $crate::stdlib::marker::PhantomData,
+                            value: self.value.recip(),
+                        }
+                    }
+
                     /// Takes the square root of a number. Returns `NaN` if `self` is a negative
                     /// number.
                     ///

diff --git a/src/tests.rs b/src/tests.rs
@@ -167,6 +167,20 @@ mod system_macro {
         }
     }
 
+    quickcheck! {
+        #[cfg(feature = "std")]
+        #[allow(trivial_casts)]
+        fn recip(v: F) -> bool {
+            let a: Quantity<Q<N1, Z0>, U<F>, F> = Quantity::<Q<P1, Z0>, U<F>, F> {
+                dimension: ::stdlib::marker::PhantomData,
+                units: ::stdlib::marker::PhantomData,
+                value: v,
+            }.recip();
+
+            v.recip() == a.value
+        }
+    }
+
     quickcheck! {
         #[cfg(feature = "std")]
         #[allow(trivial_casts)]