Expose inner type in DualNum trait (#82)

Author: prehner

CHANGELOG.md

@@ -6,6 +6,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+## [0.10.1] - 2204-11-05
+## Added
+- Expose the inner type of a generalized (hyper) dual number in the `DualNum` trait. [#81](https://github.com/itt-ustutt/num-dual/pull/81)
+
 ## [0.10.0] - 2024-10-22
 ### Packaging
 - Updated `nalgebra` dependency to 0.33. [#75](https://github.com/itt-ustutt/num-dual/pull/75)

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "num-dual"
-version = "0.10.0"
+version = "0.10.1"
 authors = [
     "Gernot Bauer <[email protected]>",
     "Philipp Rehner <[email protected]>",

src/derivatives.rs

@@ -7,6 +7,13 @@ macro_rules! impl_derivatives {
         {
             const NDERIV: usize = T::NDERIV + $nderiv;
 
+            type Inner = T;
+
+            #[inline]
+            fn from_inner(inner: Self::Inner) -> Self {
+                Self::from_re(inner)
+            }
+
             #[inline]
             fn re(&self) -> F {
                 self.re.re()

src/lib.rs

@@ -117,10 +117,16 @@ pub trait DualNum<F>:
     /// Highest derivative that can be calculated with this struct
     const NDERIV: usize;
 
+    /// Type of the elements of this generalized (hyper) dual number
+    type Inner;
+
+    /// Construct a new generalized (hyper) dual number from its real part
+    fn from_inner(inner: Self::Inner) -> Self;
+
     /// Real part (0th derivative) of the number
     fn re(&self) -> F;
 
-    /// Reciprocal (inverse) of a number `1/x`.
+    /// Reciprocal (inverse) of a number `1/x`
     fn recip(&self) -> Self;
 
     /// Power with integer exponent `x^n`
@@ -243,6 +249,12 @@ macro_rules! impl_dual_num_float {
         impl DualNum<$float> for $float {
             const NDERIV: usize = 0;
 
+            type Inner = $float;
+
+            fn from_inner(inner: Self::Inner) -> Self {
+                inner
+            }
+
             fn re(&self) -> $float {
                 *self
             }