There are a lot of functions one needs to define on a custom number type to make it work just like a julia Base number. Namely, around 160 functions, with quite a few methods.

With AbstractNumbers, this is all you need to start the life of a new, wonderful Number type:

using AbstractNumbers, SpecialFunctions
using Base.Test

struct MyNumber{T} <: AbstractNumbers.AbstractNumber{T}
    number::T
end

Base.convert(::Type{Number}, x::MyNumber) = x.number
AbstractNumbers.basetype(::Type{<: MyNumber}) = MyNumber

Now, MyNumber will have all functions defined for it. :) If you need some functions to behave differently, just overload those functions with your concrete type!

Right now, the overloads of the AbstractNumber types are generated with a script that prints out the expressions as string. I purposefully decided against the usage of a macro for two reasons:

1. I got quickly annoyed by the stack traces and not being able to immediately see what's going on - which is much easier when having all functions written out

2. I need to dynamically extract some attributes from the functions before emitting methods for it. This needs some supervision and should just be done everytime Julia Base changes - so it shouldn't be part of a macro, hence I'm stuck with some kind of generator script anyways. Instead of mixing the macro approach with a generator approach, I just went full generator!