Improve compile-time usability (#1522)

* Add `shape_const` to fixed size matrices

* Add const to all possible fns

* Update src/base/matrix.rs

* chore: cargo fmt + changelog

* chore: bump MSRV to 1.87 (for const Vec::len).

* chore: update changelog

---------

Co-authored-by: Sébastien Crozet <sebcrozet@dimforge.com>

Author: TimTheBig

.github/workflows/nalgebra-ci-build.yml

@@ -60,7 +60,7 @@ jobs:
       - name: Select rustc  version
         uses: actions-rs/toolchain@v1
         with:
-          toolchain: 1.85.0
+          toolchain: 1.87.0
           override: true
       - uses: actions/checkout@v4
       - name: check
@@ -77,7 +77,7 @@ jobs:
       - name: Select rustc  version
         uses: actions-rs/toolchain@v1
         with:
-          toolchain: 1.85.0
+          toolchain: 1.87.0
           override: true
       - uses: actions/checkout@v4
       - name: test

CHANGELOG.md

@@ -13,7 +13,10 @@ This project adheres to [Semantic Versioning](https://semver.org/).
 
 ### Changed
 
+- Bumped MSRV to 1.87.0.
+- Renamed associated const `DimName::USIZE` to `DimName::DIM`.
 - Moved to Rust 2024 edition.
+- Several methods are now `const` whenever possible. See details in [#1522](https://github.com/dimforge/nalgebra/pull/1522).
 
 ## [0.33.2] (29 October 2024)
 

Cargo.toml

@@ -12,7 +12,7 @@ categories = ["science", "mathematics", "wasm", "no-std"]
 keywords = ["linear", "algebra", "matrix", "vector", "math"]
 license = "Apache-2.0"
 edition = "2024"
-rust-version = "1.85.0"
+rust-version = "1.87.0"
 exclude = ["/ci/*", "/.travis.yml", "/Makefile"]
 
 [badges]

src/base/cg.rs

@@ -31,7 +31,7 @@ where
     #[inline]
     pub fn new_scaling(scaling: T) -> Self {
         let mut res = Self::from_diagonal_element(scaling);
-        res[(D::dim() - 1, D::dim() - 1)] = T::one();
+        res[(D::DIM - 1, D::DIM - 1)] = T::one();
 
         res
     }
@@ -59,11 +59,8 @@ where
         SB: Storage<T, DimNameDiff<D, U1>>,
     {
         let mut res = Self::identity();
-        res.generic_view_mut(
-            (0, D::dim() - 1),
-            (DimNameDiff::<D, U1>::name(), Const::<1>),
-        )
-        .copy_from(translation);
+        res.generic_view_mut((0, D::DIM - 1), (DimNameDiff::<D, U1>::name(), Const::<1>))
+            .copy_from(translation);
 
         res
     }
@@ -364,9 +361,9 @@ impl<T: Scalar + Zero + One + ClosedMulAssign + ClosedAddAssign, D: DimName, S:
         D: DimNameSub<U1>,
         SB: Storage<T, DimNameDiff<D, U1>>,
     {
-        for i in 0..D::dim() {
-            for j in 0..D::dim() - 1 {
-                let add = shift[j].clone() * self[(D::dim() - 1, i)].clone();
+        for i in 0..D::DIM {
+            for j in 0..D::DIM - 1 {
+                let add = shift[j].clone() * self[(D::DIM - 1, i)].clone();
                 self[(j, i)] += add;
             }
         }
@@ -382,22 +379,17 @@ impl<T: Scalar + Zero + One + ClosedMulAssign + ClosedAddAssign, D: DimName, S:
         DefaultAllocator: Allocator<DimNameDiff<D, U1>>,
     {
         let scale = self
-            .generic_view(
-                (D::dim() - 1, 0),
-                (Const::<1>, DimNameDiff::<D, U1>::name()),
-            )
+            .generic_view((D::DIM - 1, 0), (Const::<1>, DimNameDiff::<D, U1>::name()))
             .tr_dot(shift);
         let post_translation = self.generic_view(
             (0, 0),
             (DimNameDiff::<D, U1>::name(), DimNameDiff::<D, U1>::name()),
         ) * shift;
 
-        self[(D::dim() - 1, D::dim() - 1)] += scale;
+        self[(D::DIM - 1, D::DIM - 1)] += scale;
 
-        let mut translation = self.generic_view_mut(
-            (0, D::dim() - 1),
-            (DimNameDiff::<D, U1>::name(), Const::<1>),
-        );
+        let mut translation =
+            self.generic_view_mut((0, D::DIM - 1), (DimNameDiff::<D, U1>::name(), Const::<1>));
         translation += post_translation;
     }
 }
@@ -419,10 +411,8 @@ where
             (0, 0),
             (DimNameDiff::<D, U1>::name(), DimNameDiff::<D, U1>::name()),
         );
-        let normalizer = self.generic_view(
-            (D::dim() - 1, 0),
-            (Const::<1>, DimNameDiff::<D, U1>::name()),
-        );
+        let normalizer =
+            self.generic_view((D::DIM - 1, 0), (Const::<1>, DimNameDiff::<D, U1>::name()));
         let n = normalizer.tr_dot(v);
 
         if !n.is_zero() {

src/base/construction.rs

@@ -792,12 +792,12 @@ R::name(), C::name();         // Arguments for `_generic` constructors.
 
 impl_constructors_from_data!(data; R, Dyn;
 => R: DimName;
-R::name(), Dyn(data.len() / R::dim());
+R::name(), Dyn(data.len() / R::DIM);
 );
 
 impl_constructors_from_data!(data; Dyn, C;
 => C: DimName;
-Dyn(data.len() / C::dim()), C::name();
+Dyn(data.len() / C::DIM), C::name();
 );
 
 #[cfg(any(feature = "std", feature = "alloc"))]

src/base/construction_view.rs

@@ -14,7 +14,7 @@ impl<'a, T: Scalar, R: Dim, C: Dim, RStride: Dim, CStride: Dim>
     /// This method is unsafe because the input data array is not checked to contain enough elements.
     /// The generic types `R`, `C`, `RStride`, `CStride` can either be type-level integers or integers wrapped with `Dyn()`.
     #[inline]
-    pub unsafe fn from_slice_with_strides_generic_unchecked(
+    pub const unsafe fn from_slice_with_strides_generic_unchecked(
         data: &'a [T],
         start: usize,
         nrows: R,
@@ -163,7 +163,7 @@ impl<'a, T: Scalar, R: Dim, C: Dim, RStride: Dim, CStride: Dim>
     /// This method is unsafe because the input data array is not checked to contain enough elements.
     /// The generic types `R`, `C`, `RStride`, `CStride` can either be type-level integers or integers wrapped with `Dyn()`.
     #[inline]
-    pub unsafe fn from_slice_with_strides_generic_unchecked(
+    pub const unsafe fn from_slice_with_strides_generic_unchecked(
         data: &'a mut [T],
         start: usize,
         nrows: R,

src/base/dimension.rs

@@ -223,7 +223,7 @@ pub struct Const<const R: usize>;
 
 /// Trait implemented exclusively by type-level integers.
 pub trait DimName: Dim {
-    const USIZE: usize;
+    const DIM: usize;
 
     /// The name of this dimension, i.e., the singleton `Self`.
     fn name() -> Self;
@@ -280,7 +280,7 @@ unsafe impl<const T: usize> Dim for Const<T> {
 }
 
 impl<const T: usize> DimName for Const<T> {
-    const USIZE: usize = T;
+    const DIM: usize = T;
 
     #[inline]
     fn name() -> Self {

src/base/iter.rs

@@ -279,7 +279,7 @@ pub struct RowIter<'a, T, R: Dim, C: Dim, S: RawStorage<T, R, C>> {
 }
 
 impl<'a, T, R: Dim, C: Dim, S: 'a + RawStorage<T, R, C>> RowIter<'a, T, R, C, S> {
-    pub(crate) fn new(mat: &'a Matrix<T, R, C, S>) -> Self {
+    pub(crate) const fn new(mat: &'a Matrix<T, R, C, S>) -> Self {
         RowIter { mat, curr: 0 }
     }
 }
@@ -330,7 +330,7 @@ pub struct RowIterMut<'a, T, R: Dim, C: Dim, S: RawStorageMut<T, R, C>> {
 }
 
 impl<'a, T, R: Dim, C: Dim, S: 'a + RawStorageMut<T, R, C>> RowIterMut<'a, T, R, C, S> {
-    pub(crate) fn new(mat: &'a mut Matrix<T, R, C, S>) -> Self {
+    pub(crate) const fn new(mat: &'a mut Matrix<T, R, C, S>) -> Self {
         RowIterMut {
             mat,
             curr: 0,

src/base/matrix.rs

@@ -408,7 +408,7 @@ where
 impl<T, R: Dim, C: Dim, S: RawStorage<T, R, C>> Matrix<T, R, C, S> {
     /// Creates a new matrix with the given data.
     #[inline(always)]
-    pub fn from_data(data: S) -> Self {
+    pub const fn from_data(data: S) -> Self {
         unsafe { Self::from_data_statically_unchecked(data) }
     }
 
@@ -1115,7 +1115,7 @@ impl<T, R: Dim, C: Dim, S: RawStorage<T, R, C>> Matrix<T, R, C, S> {
     /// }
     /// ```
     #[inline]
-    pub fn row_iter(&self) -> RowIter<'_, T, R, C, S> {
+    pub const fn row_iter(&self) -> RowIter<'_, T, R, C, S> {
         RowIter::new(self)
     }
 
@@ -1160,7 +1160,7 @@ impl<T, R: Dim, C: Dim, S: RawStorage<T, R, C>> Matrix<T, R, C, S> {
     /// assert_eq!(a, expected);
     /// ```
     #[inline]
-    pub fn row_iter_mut(&mut self) -> RowIterMut<'_, T, R, C, S>
+    pub const fn row_iter_mut(&mut self) -> RowIterMut<'_, T, R, C, S>
     where
         S: RawStorageMut<T, R, C>,
     {

src/base/matrix_view.rs

@@ -48,7 +48,7 @@ macro_rules! view_storage_impl (
             ///
             /// `*ptr` must point to memory that is valid `[T; R * C]`.
             #[inline]
-            pub unsafe fn from_raw_parts(ptr:     $Ptr,
+            pub const unsafe fn from_raw_parts(ptr:     $Ptr,
                                          shape:   (R, C),
                                          strides: (RStride, CStride))
                                         -> Self