array_view for C++11

Single header-only library of array_view, a lightweight range view class for accessing contiguous sequence of objects.

• Introduction
• Installation
• Usage
• API
• Test
• License

Introduction

array_view is a lightweight random-access range abstraction of an array slice:

double array[5] = {1, 2, 3, 4, 5};
ext::array_view<double> view{array + 1, 3}; // view of the {2, 3, 4} part

The concept is the same as that of GSL's span, but array_view uses size_t for index type for better compatibility with the standard library. I'm okay with GSL's idea of using signed index itself, but the incompatibility with the standard library really annoys me.

Installation

This library has no dependency. Just copy array_view.hpp to your include directory and you are done!

Usage

The library introduces two names in namespace ext:

• ext::array_view
• ext::make_array_view

Use ext::make_array_view() to create a view from a container object or an array. The created view then works as a random-access range and also supports slicing operations such as subview(i, n).

Example

#include <iostream>
#include <vector>
#include <array_view.hpp>

int main()
{
    std::vector<int> vector = {1, 2, 3, 4};
    ext::array_view<int> view = ext::make_array_view(vector);

    for (int& num : view.drop_last(1)) {
        std::cout << num << ' ';
    }
    std::cout << '\n';
    // Prints: 1 2 3
}

API

Container-like interface

Given an array_view object v viewing an array slice [p, p+n) and given an index i:

Expression	Result
v.empty()	n == 0
v.size()	n
v.data()	p
v[i]	*(p + i)
v.at(i)	*(p + i) with bounds check
v.front()	*p
v.back()	*(p + n - 1)
v.begin()	iterator pointing to p
v.end()	iterator pointing to p + n
v.rbegin()	reverse begin
v.rend()	reverse end

Slicing operations

Given an array_view object v with length n:

Expression	Result	Range
v.subview(i, k)	k elements from i	[0, k)
v.first(k)	first k elements	[n-k, n)
v.last(k)	last k elements	[n-k, n)
v.drop_first(k)	elements but first k	[k, n)
v.drop_last(k)	elements but last k	[0, n-k)

Comparison

All comparisons are shallow. Given array_view objects v and w:

Expression	True when
v == w	v and w view the same slice
v != w	!(v == w)

Misc.

Given array_view objects v and w:

Expression	Effect
v.swap(w)	v and w are swapped
v.as_const()	returns const view

Test

To run test, go to repository root and type following commands:

mkdir tests/build
cd tests/build
cmake ..
cmake --build .
./run

License

Boost Software License, Version 1.0.

License text is in the header file so you do not need to bundle LICENSE.txt with your project. Just copy the header file into your include directory.