Begin adding optional support for nalgebra types.

Author: adamreichold

CHANGELOG.md

@@ -1,6 +1,7 @@
 # Changelog
 
 - Unreleased
+  - Add conversions from datatypes provided by the [`nalgebra` crate](https://nalgebra.org/). ([#347](https://github.com/PyO3/rust-numpy/pull/347))
   - Drop our wrapper for NumPy iterators which were deprecated in v0.16.0 as ndarray's iteration facilities are almost always preferable. ([#324](https://github.com/PyO3/rust-numpy/pull/324))
 
 - v0.17.2

Cargo.toml

@@ -18,6 +18,7 @@ license = "BSD-2-Clause"
 ahash = "0.7"
 half = { version = "1.8", default-features = false, optional = true }
 libc = "0.2"
+nalgebra = { version = "0.31", default-features = false, optional = true }
 num-complex = ">= 0.2, < 0.5"
 num-integer = "0.1"
 num-traits = "0.2"

src/convert.rs

@@ -183,6 +183,30 @@ where
     }
 }
 
+#[cfg(feature = "nalgebra")]
+impl<N, R, C, S> ToPyArray for nalgebra::Matrix<N, R, C, S>
+where
+    N: nalgebra::Scalar + Element,
+    R: nalgebra::Dim,
+    C: nalgebra::Dim,
+    S: nalgebra::storage::Storage<N, R, C>,
+{
+    type Item = N;
+    type Dim = crate::Ix2;
+
+    fn to_pyarray<'py>(&self, py: Python<'py>) -> &'py PyArray<Self::Item, Self::Dim> {
+        unsafe {
+            let array = PyArray::new(py, (self.nrows(), self.ncols()), false);
+            for r in 0..self.nrows() {
+                for c in 0..self.ncols() {
+                    *array.uget_mut((r, c)) = self.get_unchecked((r, c)).clone();
+                }
+            }
+            array
+        }
+    }
+}
+
 pub(crate) trait ArrayExt {
     fn npy_strides(&self) -> [npyffi::npy_intp; 32];
     fn order(&self) -> Option<c_int>;

tests/to_py.rs

@@ -298,3 +298,18 @@ fn slice_container_type_confusion() {
         let _py_arr = vec![1, 2, 3].into_pyarray(py);
     });
 }
+
+#[cfg(feature = "nalgebra")]
+#[test]
+fn matrix_to_numpy() {
+    let matrix = nalgebra::Matrix3::<i32>::new(0, 1, 2, 3, 4, 5, 6, 7, 8);
+
+    Python::with_gil(|py| {
+        let array = matrix.to_pyarray(py);
+
+        assert_eq!(
+            array.readonly().as_array(),
+            array![[0, 1, 2], [3, 4, 5], [6, 7, 8]],
+        );
+    });
+}