On Monday, October 05, 2015 07:19:48 PM Jameson Nash wrote:
> in short: you can't.
In long: you can :-), but it's not recommended. There may be exactly one case
in which this happens in all of Base julia, and that was from before we had
fast tuples (yet there are still perhaps reasons to keep it). So you should be
really, really sure you want to do this.
As always, you can figure out how this works by looking at the typical
expressions, e.g.,
ex = :(immutable Foo <: GenType end)
Here's a demo:
julia> module MyModule
abstract GenType
let counter = 0
global foo
function foo()
eval(MyModule, Expr(:type, false, Expr(:<:, symbol("Foo",
counter+=1), :GenType), :()))
end
end
export foo
end
WARNING: replacing module MyModule
MyModule
julia> MyModule.Foo1
ERROR: UndefVarError: Foo1 not defined
julia> MyModule.foo()
julia> MyModule.Foo1
MyModule.Foo1
julia> MyModule.Foo2
ERROR: UndefVarError: Foo2 not defined
julia> MyModule.foo()
julia> MyModule.Foo2
MyModule.Foo2
--Tim
>
> alternatives include using a Tuple or using a Dict
>
> On Mon, Oct 5, 2015 at 2:53 PM Damien <[email protected]> wrote:
> > Hi all,
> >
> > I'm writing code in which I generate a composite type and various methods
> > based on the fields of another type.
> >
> > I can do this at the expressions level with macros, but can I also
> > generate the new type definition in a plain function using introspection?
> >
> > Best
