How to Initialize a std::vector with Specific Elements Without Loops?

How to Initialize a std::vector with Hardcoded Elements Like an Array

Initializing a std::vector with a list of hardcoded elements might seem like a hassle compared to the simplicity of initializing an array. The common approach involves iteratively pushing elements onto the vector using push_back(). But is there a more elegant solution that mirrors the concise syntax of array initialization?

C 11's Elegant Solution

If your compiler supports C 11, the answer is a resounding yes. You can directly initialize a std::vector with a list of elements enclosed in {}:

<code class="cpp">std::vector<int> v = {1, 2, 3, 4};</code>

This syntax mimics array initialization and eliminates the need for loops or push_back().

Alternatives for Older Compilers

For compilers that don't support C 11, there are alternative methods:

Boost.Assign Library:

The Boost.Assign library provides a convenient way to initialize vectors using the following syntax:

<code class="cpp">#include <boost/assign/list_of.hpp>
std::vector<int> v = boost::assign::list_of(1)(2)(3)(4);</code>

Operator Overloading:

You can overload the = operator to initialize a vector:

<code class="cpp">#include <boost/assign/std/vector.hpp>
using namespace boost::assign;
std::vector<int> v;
v += 1, 2, 3, 4;</code>

Note that this method has some performance overhead compared to direct initialization, making it less suitable for performance-critical code.

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