Implement Default trait for sparse matrix types

nalgebra-sparse/src/cs.rs

@@ -226,6 +226,15 @@ impl<T> CsMatrix<T> {
     }
 }
 
+impl<T> Default for CsMatrix<T> {
+    fn default() -> Self {
+        Self {
+            sparsity_pattern: Default::default(),
+            values: vec![],
+        }
+    }
+}
+
 impl<T: Scalar + One> CsMatrix<T> {
     #[inline]
     pub fn identity(n: usize) -> Self {

nalgebra-sparse/src/csc.rs

@@ -574,6 +574,14 @@ impl<T> CscMatrix<T> {
     }
 }
 
+impl<T> Default for CscMatrix<T> {
+    fn default() -> Self {
+        Self {
+            cs: Default::default(),
+        }
+    }
+}
+
 /// Convert pattern format errors into more meaningful CSC-specific errors.
 ///
 /// This ensures that the terminology is consistent: we are talking about rows and columns,

nalgebra-sparse/src/csr.rs

@@ -575,6 +575,14 @@ impl<T> CsrMatrix<T> {
     }
 }
 
+impl<T> Default for CsrMatrix<T> {
+    fn default() -> Self {
+        Self {
+            cs: Default::default(),
+        }
+    }
+}
+
 /// Convert pattern format errors into more meaningful CSR-specific errors.
 ///
 /// This ensures that the terminology is consistent: we are talking about rows and columns,

nalgebra-sparse/src/pattern.rs

@@ -291,6 +291,16 @@ impl SparsityPattern {
     }
 }
 
+impl Default for SparsityPattern {
+    fn default() -> Self {
+        Self {
+            major_offsets: vec![0],
+            minor_indices: vec![],
+            minor_dim: 0,
+        }
+    }
+}
+
 /// Error type for `SparsityPattern` format errors.
 #[non_exhaustive]
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]

nalgebra-sparse/tests/unit_tests/csc.rs

@@ -12,6 +12,18 @@ use crate::common::csc_strategy;
 
 use std::collections::HashSet;
 
+#[test]
+fn csc_matrix_default() {
+    let matrix: CscMatrix<f32> = CscMatrix::default();
+
+    assert_eq!(matrix.nrows(), 0);
+    assert_eq!(matrix.ncols(), 0);
+    assert_eq!(matrix.nnz(), 0);
+
+    assert_eq!(matrix.values(), &[]);
+    assert!(matrix.get_entry(0, 0).is_none());
+}
+
 #[test]
 fn csc_matrix_valid_data() {
     // Construct matrix from valid data and check that selected methods return results

nalgebra-sparse/tests/unit_tests/csr.rs

@@ -12,6 +12,18 @@ use crate::common::csr_strategy;
 
 use std::collections::HashSet;
 
+#[test]
+fn csr_matrix_default() {
+    let matrix: CsrMatrix<f32> = CsrMatrix::default();
+
+    assert_eq!(matrix.nrows(), 0);
+    assert_eq!(matrix.ncols(), 0);
+    assert_eq!(matrix.nnz(), 0);
+
+    assert_eq!(matrix.values(), &[]);
+    assert!(matrix.get_entry(0, 0).is_none());
+}
+
 #[test]
 fn csr_matrix_valid_data() {
     // Construct matrix from valid data and check that selected methods return results

nalgebra-sparse/tests/unit_tests/pattern.rs

@@ -1,5 +1,19 @@
 use nalgebra_sparse::pattern::{SparsityPattern, SparsityPatternFormatError};
 
+#[test]
+fn sparsity_pattern_default() {
+    // Check that the pattern created with `Default::default()` is equivalent to a zero-sized pattern.
+    let pattern = SparsityPattern::default();
+    let zero = SparsityPattern::zeros(0, 0);
+    
+    assert_eq!(pattern.major_dim(), zero.major_dim());
+    assert_eq!(pattern.minor_dim(), zero.minor_dim());
+    assert_eq!(pattern.major_offsets(), zero.major_offsets());
+    assert_eq!(pattern.minor_indices(), zero.minor_indices());
+
+    assert_eq!(pattern.nnz(), 0);
+}
+
 #[test]
 fn sparsity_pattern_valid_data() {
     // Construct pattern from valid data and check that selected methods return results

src/base/vec_storage.rs

@@ -31,6 +31,46 @@ pub struct VecStorage<T, R: Dim, C: Dim> {
     ncols: C,
 }
 
+impl<T> Default for VecStorage<T, Dyn, Dyn> {
+    fn default() -> Self {
+        Self {
+            data: vec![],
+            nrows: Dyn::from_usize(0),
+            ncols: Dyn::from_usize(0),
+        }
+    }
+}
+
+impl<T, R: DimName> Default for VecStorage<T, R, Dyn> {
+    fn default() -> Self {
+        Self {
+            data: vec![],
+            nrows: R::name(),
+            ncols: Dyn::from_usize(0),
+        }
+    }
+}
+
+impl<T, C: DimName> Default for VecStorage<T, Dyn, C> {
+    fn default() -> Self {
+        Self {
+            data: vec![],
+            nrows: Dyn::from_usize(0),
+            ncols: C::name(),
+        }
+    }
+}
+
+impl<T: Default, R: DimName, C: DimName> Default for VecStorage<T, R, C> {
+    fn default() -> Self {
+        let nrows = R::name();
+        let ncols = C::name();
+        let mut data = Vec::new();
+        data.resize_with(nrows.value() * ncols.value(), Default::default);
+        Self { data, nrows, ncols }
+    }
+}
+
 #[cfg(feature = "serde-serialize")]
 impl<T, R: Dim, C: Dim> Serialize for VecStorage<T, R, C>
 where