Re: [julia-users] Re: Using macros to override lots of operators for a user-defined type

['Greg Plowman' via julia-users]

I have exactly the same requirement. 
Additionally, I often have more than 2 fields and also change the fields of 
my custom types.

So I use a slightly more general version of the above:


function CompositeBinaryOp(T::Symbol, op::Symbol)
    expressions = [ :($op(x1.$field, x2.$field)) for field in 
fieldnames(eval(T)) ]
    body = Expr(:call, T, expressions...)
    quote
        function $op(x1::$T, x2::$T)
            return $body
        end
    end
end

type M
    a
    b
end

import Base: +, -, *, /, ^

for T in [:M]
    for op in [:+, :-, :*, :/, :^]
        #eval(CompositeBinaryOp(T, op))

        code = CompositeBinaryOp(T, op)
        println(code, "\n")
        eval(code)
    end
end

 
The advantage here for me is that I can change the fields (number, type 
order etc.) and operators don't need manual updating.

I have similar functions for copy constructors, unary operators etc.