I'm just into metaprogramming and was watching Cppcon channel on youtube, and saw this std::integral_constant, but cannot find its use.

As far as i understood, it is a way to "pack" a value along with its type, it can be instantiated with

std::integral_constant<int, 42> i;
std::integral_constant<bool, true> b;
std::integral_constant<float, 3.14> f;
...

and each of those instances can be used just like the value they contains, i.e.: can be passed around, used in math operations, comparisons, etc.

But i cannot understand why should i use those structs instead of the actual contained values, nor if i can actually access the value type (i.e.: int, bool and float) at runtime to do stuff with it.

Can someone present a simple example of practical use of this feature? An example that explain its usage difference from using the actual values?