Do templates shorten the size of source or binary or both

Question

I read that templates are complied into different entities so does that mean the binary size will be same as we have complied it using different functions?

Answer 1

They should shorten the source size (if they are reused) but not the binary size (the template is compiled for each different instantiation).

This differs from Java generics, where there is a full type erasure (generics only serve as a compile time verification of types) or C#, where generics are compiled into specific binaries that can be directly reused without having to recompile and generate more code.

Answer 2

My understanding is that for each type you instantiate with a template the complier produces the relevant class to match that type - so if you use List<int>, List<foo> and List<float> there will effectively be three different List classes in your complied binary.

Edit:
What I didn't explicitly state was that I'm inferring that merging several classes in to a single template will (probably) not reduce the size of your binary, but should reduce the size of your source.