fix #283: add possibility to include num-traits/libm for sin and cos …

…in no_std builds

Cargo.toml

@@ -85,6 +85,8 @@ use_serde = ["serde"]
 rational-support = ["num-rational"]
 bigint-support = ["num-bigint", "num-rational/num-bigint-std"]
 complex-support = ["num-complex"]
+# enable sin/cos for no_std build via libm
+libm = [ "num-traits/libm" ]
 
 [[example]]
 name = "base"

src/features.rs

@@ -81,11 +81,11 @@ macro_rules! si {
     ($($tt:tt)*) => {};
 }
 
-/// Expands the given block of code when `uom` is compiled with the `std` feature.
+/// Expands the given block of code when `uom` is compiled with either `std` or `libm` feature.
 #[doc(hidden)]
 #[macro_export]
-#[cfg(feature = "std")]
-macro_rules! std {
+#[cfg(any(feature = "std", feature = "libm"))]
+macro_rules! std_or_libm {
     ($($tt:tt)*) => { $($tt)* };
 }
 

src/lib.rs

@@ -97,6 +97,7 @@
 //!    `uom` with `no_std`. Enabled by default.
 //!  * `use_serde` -- Feature to enable support for serialization and deserialization of quantities
 //!    with the [Serde][serde] crate. Disabled by default.
+//!  * `libm` -- Enable use of trigonometrical functions (sin, cos, ...) on no_std targets
 //!
 //!    [Serde][serde] support for the `big*` and `rational*` underlying storage types requires
 //!    manually enabling the `serde` feature for the `num-rational` and `num-bigint` crates. To do
@@ -277,9 +278,9 @@ pub mod lib {
 // Conditionally import num sub-crate types based on feature selection.
 #[doc(hidden)]
 pub mod num {
-    #[cfg(feature = "std")]
+    #[cfg(any(feature = "std", feature = "libm"))]
     pub use num_traits::float::Float;
-    #[cfg(not(feature = "std"))]
+    #[cfg(not(any(feature = "std", feature = "libm")))]
     pub use num_traits::float::FloatCore as Float;
 
     pub use num_traits::{pow, FromPrimitive, Num, One, Saturating, Signed, ToPrimitive, Zero};

src/si/angle.rs

@@ -1,6 +1,6 @@
 //! Angle (dimensionless quantity).
 
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "libm"))]
 use super::ratio::Ratio;
 
 quantity! {
@@ -64,7 +64,7 @@ impl Angle<crate::si::SI<f64>, f64> {
 }
 
 /// Implementation of various stdlib trigonometric functions
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "libm"))]
 impl<U, V> Angle<U, V>
 where
     U: crate::si::Units<V> + ?Sized,
@@ -121,7 +121,7 @@ where
     }
 }
 
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "libm"))]
 impl<D, U, V> crate::si::Quantity<D, U, V>
 where
     D: crate::si::Dimension + ?Sized,
@@ -161,7 +161,7 @@ mod tests {
         }
     }
 
-    #[cfg(feature = "std")]
+    #[cfg(any(feature = "std", feature = "libm"))]
     mod trig {
         storage_types! {
             types: Float;

src/si/ratio.rs

@@ -1,6 +1,6 @@
 //! Ratio (dimensionless quantity).
 
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "libm"))]
 use super::angle::{Angle, radian};
 
 quantity! {
@@ -33,7 +33,7 @@ quantity! {
 }
 
 /// Implementation of various stdlib functions.
-#[cfg(feature = "std")]
+#[cfg(any(feature = "std", feature = "libm"))]
 impl<U, V> Ratio<U, V>
 where
     U: crate::si::Units<V> + ?Sized,
@@ -220,7 +220,7 @@ mod tests {
         }
     }
 
-    #[cfg(feature = "std")]
+    #[cfg(any(feature = "std", feature = "libm"))]
     mod float {
         storage_types! {
             types: Float;

src/system.rs

@@ -611,7 +611,7 @@ macro_rules! system {
                 self.value.classify()
             }
 
-            std! {
+            std_or_libm! {
             autoconvert! {
             /// Calculates the length of the hypotenuse of a right-angle triangle given the legs.
             #[must_use = "method returns a new number and does not mutate the original value"]
@@ -807,7 +807,7 @@ macro_rules! system {
                         self.value.is_normal()
                     }
 
-                    std! {
+                    std_or_libm! {
                     /// Takes the cubic root of a number.
                     ///
                     #[cfg_attr(all(feature = "si", feature = "f32"), doc = " ```rust")]