Algorithm helpers - kdalgorithms

The purpose of this library is to make it easier to work with algorithms in C++14 and up.

Example - filtered

With C++11 algorithms you might write:

std::vector<int> result;
auto is_odd = [] (int i) {return i % 2 == 1; };
std::copy_if(my_list.cbegin(), my_list.cend(), std::back_inserter(result), is_odd);

With this library you can instead write:

auto is_odd = [] (int i) {return i % 2 == 1; };
auto result = kdalgorithms::filtered(my_list, is_odd);

Observe that it:

takes a complete collection rather than an iterator pairs
returns the result rather than taking an iterator to where it should go

Example - max_value_less_than

When searching in a collection for the largest element no larger than a given value, a good algorithmic choice is std::upper_bound, or ... is it std::lower_bound, and what exactly does is return?

Here is how to do it with this library:

std::optional<int> result = kdalgorithms::max_value_less_than(int_vector, 4);

By returning an optional rather than an iterator, you do not need to worry whether you should check it against int_vector.begin() or int_vector.cbegin(). It is also more obvious that the value might be non-existent - after all, that is what std::optional is all about.

Combining Algorithms

kdalgorithms offers and, or and not operators, which makes it possible to write code like this:

using namespace kdalgorithms::Operators;
std::vector<int> vec{1, 2, 3, 4, 5, 6, 7, 8, 9, 10};
const auto is_odd = [](int num) { return num % 2 == 1; };
const auto is_greather_than = [](int num) { return [num](int value) { return value > num; }; };
const auto is_dividable_by = [](int num) {
    return [num](int value) { return value % num == 0; };
};

auto result = kdalgorithms::filtered(vec, is_odd || (is_greather_than(5) && !is_dividable_by(3)));

Using member functions as predicates

Throughout the documentation we will used lambda expressions for predicates and comparison methods given to algorithms. It is, however, also possible to use pointer to member functions:

struct S
{
    int x;
    int y;
    bool hasEqualKeyValuePair() const { return x == y; }
};
std::vector<Struct> vec{{2, 3}, {1, 1}, {2, 2}, {4, 1}};
kdalgorithms::erase_if(vec, &Struct::hasEqualKeyValuePair);

Be aware though that the method must be const.

Lots of Examples

In this document you will find lots of examples. More, however, may be found in the unit tests.

Qt

kdalgorithms supports all of Qt's containers, with the exception that with Qt5 QSet isn't supported.

KDAB / KDAlgorithms