Slice

Slice

Version: v0.2.0

Status: Complete

Header: include/stratax/core/Slice.hpp

---

Overview

stratax::core::Slice represents a half-open strided one-dimensional index range.

It stores signed start, stop, and non-zero step values and is used by slicing ops for vectors, matrices, and tensors.

---

Responsibilities

Slice is responsible for:

• Storing half-open interval metadata ([start, stop)) with stride
• Enforcing the non-zero-step invariant
• Computing selected element count (size()) for positive and negative strides

Slice is not responsible for:

• Validating bounds against a concrete container extent
• Copying or materializing sliced outputs
• Multidimensional slicing policy

---

Relationships

stratax::core::Slice
├── start_ : std::ptrdiff_t
├── stop_  : std::ptrdiff_t
└── step_  : std::ptrdiff_t

Depends on:

• include/stratax/core/Exceptions.hpp

Used by:

• include/stratax/core/ops/Slice.hpp

---

Internal Data

Member	Description
start_	Inclusive start index
stop_	Exclusive stop index
step_	Non-zero stride

---

Invariants

The following conditions are always true:

• Interval semantics are half-open: [start(), stop()).
• step() is never zero.
• size() returns 0 when interval direction and bounds select no indices.
• empty() is equivalent to size() == 0.

---

Public Interface

Constructor

Slice(std::ptrdiff_t start, std::ptrdiff_t stop, std::ptrdiff_t step = 1);

Creates a strided half-open range.

Throws

• Exceptions::IndexError if step == 0

Complexity

• O(1)

---

Accessors

[[nodiscard]] std::ptrdiff_t start() const noexcept;
[[nodiscard]] std::ptrdiff_t stop() const noexcept;
[[nodiscard]] std::ptrdiff_t step() const noexcept;
[[nodiscard]] std::size_t size() const noexcept;
[[nodiscard]] bool empty() const noexcept;

Returns interval metadata and computed selection size.

Complexity

• start() / stop() / step() / empty(): O(1)
• size(): O(1)

---

Comparisons

[[nodiscard]] bool operator==(const Slice& other) const noexcept;
[[nodiscard]] bool operator!=(const Slice& other) const noexcept;

Two slices are equal when start, stop, and step all match.

Complexity

• O(1)

---

Complexity Summary

Operation	Complexity
Construction	O(1)
start() / stop() / step()	O(1)
size() / empty()	O(1)
operator== / operator!=	O(1)

---

Examples

const stratax::core::Slice every_other(0, 10, 2);  // 0,2,4,6,8
const stratax::core::Slice reverse(8, -1, -2);     // 8,6,4,2,0
 
if (!every_other.empty())
{
    const auto count = every_other.size();
    (void)count;
}

---

Design Notes

Slice keeps only local interval semantics; extent normalization and clamping happen in ops-level slicing helpers where container shape is available.

Using signed fields enables Python-like negative-index flows at higher layers without forcing unsigned conversion too early.

---

Future Improvements

• Add convenience creators for common ranges (for example full-range helpers).
• Consider optional utilities for composing/intersecting slices.

---

See Also

• include/stratax/core/ops/Slice.hpp