Merge pull request #58 from termoshtt/into_real

Convert f64 to Scalar

Author: termoshtt

src/types.rs

@@ -35,18 +35,50 @@ pub trait Scalar
     + Conjugate
     + RandNormal
     + Debug {
+    fn from_f64(f64) -> Self;
 }
 
-impl Scalar for f32 {}
-impl Scalar for f64 {}
-impl Scalar for c32 {}
-impl Scalar for c64 {}
+impl Scalar for f32 {
+    fn from_f64(f: f64) -> Self {
+        f as f32
+    }
+}
 
-pub trait RealScalar: Scalar + Float + Sum {}
+impl Scalar for f64 {
+    fn from_f64(f: f64) -> Self {
+        f
+    }
+}
+
+impl Scalar for c32 {
+    fn from_f64(f: f64) -> Self {
+        Self::new(f as f32, 0.0)
+    }
+}
 
+impl Scalar for c64 {
+    fn from_f64(f: f64) -> Self {
+        Self::new(f, 0.0)
+    }
+}
+
+pub trait RealScalar: Scalar + Float + Sum {}
 impl RealScalar for f32 {}
 impl RealScalar for f64 {}
 
+/// Convert `f64` into `Scalar`
+///
+/// ```rust
+/// use ndarray_linalg::*;
+/// fn mult<A: Scalar>(a: A) -> A {
+///     // a * 2.0  // Error!
+///     a * into_scalar(2.0)
+/// }
+/// ```
+pub fn into_scalar<T: Scalar>(f: f64) -> T {
+    T::from_f64(f)
+}
+
 /// Define associating real float type
 pub trait AssociatedReal: Sized {
     type Real: RealScalar;