Thanks for responding. Yes, I think I will do it your way. I was initially
hoping there would be a neat way to duplicate how R would do it, ie, with
keyword arguments typically always strings or numbers since this is what
many new users will be familiar with, but maybe in the end it would just be
setting a bad example.
Cheers,
Colin
On 24 June 2015 at 19:31, Milan Bouchet-Valat <nalimi...@club.fr> wrote:
> Le mercredi 24 juin 2015 à 01:18 -0700, colintbow...@gmail.com a écrit
> :
> > Hi all,
> >
> > I've got an issue I don't really like in one of my modules, and I was
> > wondering the best thing (if anything) to do about it.
> >
> > The module if for dependent bootstraps, but the problem is more of a
> > project design issue. I have a type for each bootstrap method, e.g.
> > `StationaryBootstrap`, `MovingBlockBootstrap` e.t.c. and they are all
> > sub-types of an abstract `BootstrapMethod`. Then I have functions
> > that can be called over these different bootstrap method types and
> > multiple dispatch will make sure the appropriate code is called, e.g
> > `bootindices(::StationaryBootstrap)` or
> > `bootindices(::MovingBlockBootstrap)`. This all works nicely.
> >
> > I now want to define some keyword wrapper type functions in the
> > module for users who don't want to learn much about how the types
> > within the module work. For example, my wrapper might let the user
> > describe the bootstrap procedure they want with a string, eg
> > `bootindices(...; bootstrapmethod::ASCIIString="stationary")`.
> >
> > The keyword wrapper is called, and I have a variable
> > `bootstrapMethod` which is a string. I need to convert it into the
> > appropriate bootstrap method type so I can then call the appropriate
> > method via multiple dispatch. Currently I have one function that does
> > this and looks something like this:
> >
> > function boot_string_to_type(x::ASCIIString)
> > x == "stationary" && return(StationaryBootstrap())
> > x == "movingBlock" && return(MovingBlock())
> > ...
> > end
> >
> > The problem is that this function is not type-stable.
> >
> > Should I be worried? Does anyone have a better way of dealing with
> > this kind of issue? Maybe something involving symbols or expressions,
> > or anonymous functions etc?
> >
> > Note, the situation can sometimes get quite a bit more complicated
> > than this, with multiple key-word arguments, all of which need to be
> > combined into the constructor for the relevant type.
> I think the most Julian way to do this is to have users pass a type
> instead of a string. They would write
> bootindices{T<:BootstrapMethod}(...; method::Type{T}=StationaryBootstrap)
>
> That's simpler for the user as passing a string (since autocompletion w
> ill work), you don't need to define boot_string_to_type(), and it's
> type-stable. This is the idiom used by fit() in StatsBase.jl (and
> GLM.jl) to choose which type of model should be estimated.
>
>
> Hope this helps
>
>
> PS: in the cases where you still want to pass a string as an argument,
> rather than a type, consider using symbols instead, as it is more
> efficient.
>
