from_row_iterator added

src/base/allocator.rs

@@ -41,6 +41,13 @@ pub trait Allocator<T, R: Dim, C: Dim = U1>: Any + Sized {
         ncols: C,
         iter: I,
     ) -> Self::Buffer;
+
+    /// Allocates a buffer initialized with the content of the given row-major order iterator.
+    fn allocate_from_row_iterator<I: IntoIterator<Item = T>>(
+        nrows: R,
+        ncols: C,
+        iter: I,
+    ) -> Self::Buffer;
 }
 
 /// A matrix reallocator. Changes the size of the memory buffer that initially contains (`RFrom` ×

src/base/construction.rs

@@ -86,6 +86,17 @@ where
         Self::from_data(DefaultAllocator::allocate_from_iterator(nrows, ncols, iter))
     }
 
+    /// Creates a matrix with all its elements filled by an row-major order iterator.
+    #[inline]
+    pub fn from_row_iterator_generic<I>(nrows: R, ncols: C, iter: I) -> Self
+    where
+        I: IntoIterator<Item = T>,
+    {
+        Self::from_data(DefaultAllocator::allocate_from_row_iterator(
+            nrows, ncols, iter,
+        ))
+    }
+
     /// Creates a matrix with its elements filled with the components provided by a slice in
     /// row-major order.
     ///
@@ -479,6 +490,36 @@ macro_rules! impl_constructors(
             Self::from_iterator_generic($($gargs, )* iter)
         }
 
+        /// Creates a matrix or vector with all its elements filled by a row-major iterator.
+        ///
+        /// The output matrix is filled row-by-row.
+        ///
+        /// ## Example
+        /// ```
+        /// # use nalgebra::{Matrix2x3, Vector3, DVector, DMatrix};
+        /// # use std::iter;
+        ///
+        /// let v = Vector3::from_row_iterator((0..3).into_iter());
+        /// // The additional argument represents the vector dimension.
+        /// let dv = DVector::from_row_iterator(3, (0..3).into_iter());
+        /// let m = Matrix2x3::from_row_iterator((0..6).into_iter());
+        /// // The two additional arguments represent the matrix dimensions.
+        /// let dm = DMatrix::from_row_iterator(2, 3, (0..6).into_iter());
+        ///
+        /// // For Vectors from_row_iterator is identical to from_iterator
+        /// assert!(v.x == 0 && v.y == 1 && v.z == 2);
+        /// assert!(dv[0] == 0 && dv[1] == 1 && dv[2] == 2);
+        /// assert!(m.m11 == 0 && m.m12 == 1 && m.m13 == 2 &&
+        ///         m.m21 == 3 && m.m22 == 4 && m.m23 == 5);
+        /// assert!(dm[(0, 0)] == 0 && dm[(0, 1)] == 1 && dm[(0, 2)] == 2 &&
+        ///         dm[(1, 0)] == 3 && dm[(1, 1)] == 4 && dm[(1, 2)] == 5);
+        /// ```
+        #[inline]
+        pub fn from_row_iterator<I>($($args: usize,)* iter: I) -> Self
+            where I: IntoIterator<Item = T> {
+            Self::from_row_iterator_generic($($gargs, )* iter)
+        }
+
         /// Creates a matrix or vector filled with the results of a function applied to each of its
         /// component coordinates.
         ///

src/base/default_allocator.rs

@@ -80,6 +80,40 @@ impl<T: Scalar, const R: usize, const C: usize> Allocator<T, Const<R>, Const<C>>
         //         yielded enough elements to initialize our matrix.
         unsafe { <Self as Allocator<T, Const<R>, Const<C>>>::assume_init(res) }
     }
+
+    #[inline]
+    fn allocate_from_row_iterator<I: IntoIterator<Item = T>>(
+        nrows: Const<R>,
+        ncols: Const<C>,
+        iter: I,
+    ) -> Self::Buffer {
+        #[cfg(feature = "no_unsound_assume_init")]
+        let mut res: Self::Buffer = unimplemented!();
+        #[cfg(not(feature = "no_unsound_assume_init"))]
+        let mut res = unsafe { Self::allocate_uninitialized(nrows, ncols).assume_init() };
+        let mut count = 0;
+        let res_ptr = res.as_mut_slice();
+
+        for (i, e) in iter
+            .into_iter()
+            .take(ncols.value() * nrows.value())
+            .enumerate()
+        {
+            unsafe {
+                *res_ptr
+                    .get_unchecked_mut((i % ncols.value()) * nrows.value() + i / ncols.value()) = e;
+            }
+            // res_ptr[(i % ncols.value()) * nrows.value() + i / ncols.value()] = e;
+            count += 1;
+        }
+
+        assert!(
+            count == nrows.value() * ncols.value(),
+            "Matrix init. from row iterator: iterator not long enough."
+        );
+
+        res
+    }
 }
 
 // Dynamic - Static
@@ -128,6 +162,32 @@ impl<T: Scalar, C: Dim> Allocator<T, Dynamic, C> for DefaultAllocator {
 
         VecStorage::new(nrows, ncols, res)
     }
+
+    #[inline]
+    fn allocate_from_row_iterator<I: IntoIterator<Item = T>>(
+        nrows: Dynamic,
+        ncols: C,
+        iter: I,
+    ) -> Self::Buffer {
+        let it = iter.into_iter().take(nrows.value() * ncols.value());
+        let mut res: Vec<T> = Vec::with_capacity(nrows.value() * ncols.value());
+        let res_ptr = res.as_mut_ptr();
+        let mut count = 0;
+
+        unsafe {
+            for (i, e) in it.enumerate() {
+                *res_ptr.add((i % ncols.value()) * nrows.value() + i / ncols.value()) = e;
+                count += 1;
+            }
+            res.set_len(nrows.value() * ncols.value());
+        }
+        assert!(
+            count == nrows.value() * ncols.value(),
+            "Matrix init. from row iterator: iterator not long enough."
+        );
+
+        VecStorage::new(nrows, ncols, res)
+    }
 }
 
 // Static - Dynamic
@@ -176,6 +236,32 @@ impl<T: Scalar, R: DimName> Allocator<T, R, Dynamic> for DefaultAllocator {
 
         VecStorage::new(nrows, ncols, res)
     }
+
+    #[inline]
+    fn allocate_from_row_iterator<I: IntoIterator<Item = T>>(
+        nrows: R,
+        ncols: Dynamic,
+        iter: I,
+    ) -> Self::Buffer {
+        let it = iter.into_iter().take(nrows.value() * ncols.value());
+        let mut res: Vec<T> = Vec::with_capacity(nrows.value() * ncols.value());
+        let res_ptr = res.as_mut_ptr();
+        let mut count = 0;
+
+        unsafe {
+            for (i, e) in it.enumerate() {
+                *res_ptr.add((i % ncols.value()) * nrows.value() + i / ncols.value()) = e;
+                count += 1;
+            }
+            res.set_len(nrows.value() * ncols.value());
+        }
+        assert!(
+            count == nrows.value() * ncols.value(),
+            "Matrix init. from row iterator: iterator not long enough."
+        );
+
+        VecStorage::new(nrows, ncols, res)
+    }
 }
 
 /*