Not sure if this is helpful.
Not sure if it is a good idea in general.
Certainly unsure if it is Julian.
However, I find it useful because I can change fields of my type (reorder,
add, remove, rename etc) quite easily.
macro CallDefaultConstructor(T)
expressions = [ :($field) for field in names(eval(T)) ]
return Expr(:call, T, expressions...)
end
type Parameters
sigma::Real
xi::Real
eta::Real
beta::Real
rho::Real
agrid::FloatRange
end
function Parameters()
eta = 3
sigma = 1
rho = 5
xi = 2
agrid = linrange(1,10,10)
beta = 4
@CallDefaultConstructor Parameters
end
p = Parameters()
On Saturday, January 17, 2015 at 11:34:19 AM UTC+11, Andrew wrote:
> Suppose I have a model which contains many parameters. I'd like to store
> my parameters in a type, for example
>
> type Parameters
> sigma::Real
> xi::Real
> eta::Real
> beta::Real
> rho::Real
> agrid::FloatRange
> end
>
>
> and then I need to assign some values to my parameters. The natural way I
> see to do this is
>
> params = Parameters(1,2,3,4,5,linrange(1,10,10))
>
>
>
> or something like that. However, the fact that I need to remember the
> order in which I defined these parameters means there is some chance of
> error. In reality I have about 20 parameters, so defining them this way
> would be quite annoying.
>
> It would be nice if there was a constructor that would let me use keyword
> arguments, as in
>
> params = Parameters(sigma=1,xi=2,eta=3,beta=4,rho=5,agrid=linrange(1,10,10
> )) .
>
>
>
> I know I could write my own constructor and use keyword arguments, but
> then I think I'd still need to use the ordered constructor to write that
> one.
>
> Is there an easy way to do this? Maybe a macro that could automatically
> define a constructor with keyword arguments?(I don't know much about
> metaprogramming). Alternatively, is there is a cleaner way to store
> parameters that doesn't use types?
>
> ---
> I did find a related post here.
> https://groups.google.com/forum/#!searchin/julia-users/constructor$20keyword$20arguments/julia-users/xslxrihfO30/jV2awP5tbpEJ
>
> . Someone suggests that you can define a constructor like,
> Foo(;bar=1, baz=2) = new(bar, baz)
>
> which does what I want. Is there a way to macro that so that it's
> automatically defined for every field in the type?
>
