array_view2d is a two-file header-only library to provide a two-dimensional view on a one-dimensional array or vector. The library is inspired on array_view [1] and can be used with C++98 and later and with Visual C++ 6 (VC6). With C++11 array_view2d provides a unified way to reference an array or vector (see example).

Contents

• Example usage
• In a nutshell
• License
• Dependencies
• Installation
• Synopsis
• Reported to work with
• C++ standard proposals on array views
• Notes and references

#include "array_view2d.hpp"
#include "array_view2d_output.hpp"

#include <iostream>

struct packet
{
    std::size_t dim;
    std::vector<int> data;
};

packet produce()
{
    return { 3, { 0,0, 1,1, 2,2 } };
}

int main()
{
    auto pack = produce();
    auto view = nonstd::make_view2d( pack.data, pack.dim );

    for ( auto pos : view.as_rows() )
    {
        std::cout << pos << "\n";
    }
}

prompt>g++ -Wall -std=c++11 -o example.exe example.cpp && example
{ 0, 0 }
{ 1, 1 }
{ 2, 2 }

Here is the same example expressed in C++98.

array_view2d ...

Features and properties of array_view2d are ease of installation (single header), ...

Not provided are ...

array_view2d uses the Boost Software License.

array_view2d has no other dependencies than the C++ standard library.

array_view2d is a two-file header-only library. Put array_view2d.hpp and array_view2d_output.hpp directly into the project source tree or somewhere reachable from your project.

Contents
Types in namespace nonstd
Interface of array_view2d
Algorithms for array_view2d
Macros to control error reporting

array_view2d can perform sanity checks on construction and perform bound checking on methods such as row(). Sanity checks in constructors use the same mechanism as implicit bound checks explained below.

array_view2d provides two approaches to bound checking:

• explicitly when calling row(check_bound, n) and
• implicitly when using row(n).

The explicit variants with the check_bound_t parameter throw a std::out_of_range exception when a parameter is out of bound.

The implicit variants without the check_bound_t parameter, behave in the following way:

• Assert that a parameter is within bounds; this is the default for debug builds.
• Throw an exception when a parameter violates its bounds, see av_FEATURE_EXPECT_THROWS.
• Do not check for bound violation; this is the default for release build, see av_FEATURE_EXPECT_NOP.
• Perform a user-specified action, see av_EXPECT.

The following macros control boundary checking behaviour for methods that don't use check_bound_t.

-Dav_FEATURE_EXPECT_NOP=0
Define this to 1 to turn off boundary checking assertions. Default is 0.

-Dav_FEATURE_EXPECT_ASSERTS=1
At default, boundary checks assert. Default is 1.
Turn it off by defining av_FEATURE_EXPECT_NOP.
Use exceptions instead by defining av_FEATURE_EXPECT_THROWS.
Note that the assertion mechanism is active in debug builds, not in release builds.

-Dav_FEATURE_EXPECT_THROWS=0
Define this to 1 to activate boundary checking exceptions. Default is 0.
When an out of bounds error occurs, a std::out_of_range exception is thrown.
When a sanity check fails, a std::runtime_error exception is thrown.

-Dav_EXPECT( expr, excpt, note )
Define this macro to specify boundary checking behaviour, e.g.:

#define av_EXPECT( expr, excpt, note )  assert( ( expr ) && note )

Defining av_EXPECT deactivates macros av_FEATURE_EXPECT_NOP, av_FEATURE_EXPECT_ASSERTS and av_FEATURE_EXPECT_THROWS.

array_view2d is reported to work with the following compilers:

• Visual C++ 6 SP6 (VS6), VC10, (VS2010), VC11 (VS2012), VC12 (VS2013)
• GNUC 4.8.1 with -std=c++98, -std=c++03, -std=c++11, -std=c++1y
• clang 3.4 with -std=c++03, -std=c++11 (on Travis)

At the time of writing there are two proposals for the C++ standard on providing multidimensional views on arrays [2-4]. These proposals take a general approach to dimensionality, whereas array_view2d restricts itself to unstrided rows and slices.

[1] array_view.
[2] N3851: Multidimensional bounds, index and array_view (PDF).
[3] N4346: Multidimensional bounds, index and array_view, revision 6.
[4] N4355: Shared Multidimensional Array with Polymorphic Layout (PDF).