Question

If I make some code like this:

boost::array<10> a1;
boost::array<20> a2;
boost::array<30> a3;

Will the template generate 3 different classes for me and make the size of my code grow?

If it does, is the compiler/linker smart enough to only include the methods definitions of what I’m actually using? For example: if I use the method ‘at’ of the a1 object, but never user the method ‘at’ of the a2 object, then the ‘at’ of the a2 would be totally discarded.

Answer 1

Will the template generate 3 different classes for me

Yes; every instantiation of a template with different template arguments in in effect a different type.

and make the size of my code grow?

Extremely unlikely, certainly no worse than enabling inlining does.

If it does, is the compiler/linker smart enough to only include the methods definitions of what I’m actually using?

Yes, unless you explicitly instantiate the type as a whole.

For example: if I use the method ‘at’ of the a1 object, but never user the method ‘at’ of the a2 object, then the ‘at’ of the a2 would be totally discarded.

If you never use the method at of a2, and you didn’t explicitly instantiate boost::array<T, 20> as a whole, then boost::array<T, 20>::at() is never instantiated to begin with and there’s nothing to discard.