Shape

Shape

Header: include/stratax/core/Shape.hpp.

Shape owns unsigned dimensions in outermost-to-innermost order. It stores metadata, not array values, and computes element counts and canonical row-major strides. Public dimension access and iterators are read-only.

Construction and ownership

Default construction produces rank zero. Initializer-list and vector constructors copy dimensions, including zero extents. They do not compute every possible shape product during construction. Copying duplicates dimension storage; copy assignment has Buffer's strong exception guarantee. Moving leaves a distinct source rank zero; self-move leaves it unchanged. swap exchanges storage without copying and preserves references under the new owner.

Queries and errors

API	Behavior	Cost
rank	Number of stored dimensions	O(1)
empty	Whether rank is zero, not whether elements is zero	O(1)
elements	Product, or zero for rank zero/any zero extent	O(r)
strides	New Shape; last stride one, earlier strides are right-side products	O(r)
operator[]	Unchecked dimension access	O(1)
at	Checked signed access with negative indices	O(1)
begin/end and const/reverse variants	Read-only contiguous traversal	O(1) acquisition
==, !=	Same rank and dimensions	O(r) worst case

An invalid at index raises Exceptions::IndexError. elements detects nonzero product overflow with DimensionError and returns zero if any extent is zero, even when an earlier prefix would overflow. strides checks each right-side product separately and can throw even for a shape with zero total elements. Both zero rank and zero extents are valid. No inferred negative dimensions exist.

#include <stratax.h>
#include <cassert>
 
int main() {
    const stratax::core::Shape shape{2, 3, 4};
    assert(shape.elements() == 24);
    assert(shape.strides() == stratax::core::Shape({12, 4, 1}));
    assert(shape.at(-1) == 4);
    const stratax::core::Shape zero{2, 0, 4};
    assert(!zero.empty() && zero.elements() == 0);
    assert(stratax::core::Shape{}.empty());
}

Shape prints tuple notation: (2, 3, 4), (5,), or (). Construction/copying and allocation cost O(r); copy assignment also destroys old metadata. Allocation failures propagate. Move construction and swap are O(1).