[nem-en] Late Binding in Nemerle

[Kamil Skalski]

Generating such proxy classes should be relatively easy using a macro.
def x = dynamic_implement (obj, IFoo, IBar, IWazz);
x.foo();
x.bar();

would be quite nice. :)

dynamic_implement would generate a class implementing IFoo, IBar,
IWazz (maybe doing some caching to avoid generating the same proxy
classes several times) and create its instance.

2006/7/2, Arthur Peters <amp at singingwizard.org>:
> This is quite cool. I've been a Python programmer in the past so the
> ability to do duck typing when needed could be really nice.
>
> I ran across a page about duck typing in Java. It provides a class that
> can take an object and return a proxy object that implements an
> interface you give even if the original object did not.
> ( http://www.coconut-palm-software.com/the_visual_editor/?p=25 )
>
> This seems like it could be nice in addition to your macro, because it
> would allow you to pass the proxy into places that don't know about the
> whole duck typing thing. Also it provides a middle ground: You can
> access functions based on only name and signature and you have the type
> safety provided by a defined interface.
>
> I think it would be possible in .NET, but it looks complicated because
> you would need to generate IL opcodes to create the proxy.
>
> If people think this would be useful I will take a crack at implementing
> it.
>
> Thanks for the good work, everyone!
> -Arthur
>
> On Sat, 2006-07-01 at 18:33 +0400, Snaury wrote:
> > Hi everyone,
> >
> > I was trying to grok nemerle's macros for some time when an idea
> > suddenly popped in my mind how I could do late binding aka dynamic
> > typing aka duck typing in a pretty simple and (maybe?) rich way. So I
> > wrote a macro for this, source code here:
> > http://www.furry.ru/kitsu/nemerle/Kitsu.LateBindingMacro.n.txt
> >
> > It allows to use late binding on (I think) any expression, you just
> > have to wrap it with late, and use like this:
> >
> >   late(expr).CallMe(param1, param2, param3).CallOtherMe(param, param,
> > param).Property[param, param, param] = value
> >
> > It also supports ref/out and named parameters:
> >
> >   late(expr).CallMe(namedparameter = ref variable, out variable, and
> > the like...)
> >
> > though one needs to be very careful with named parameters, because
> > when you name a parameter, other (unnamed) parameters might get
> > shifted, for example in function:
> >
> >   public void SomeFunc(a : int, b : int) : void
> >
> > when you use
> >
> >   late(obj).SomeFunc(v1, a = v2)
> >
> > SomeFunc will be called as SomeFunc(v2, v1), i.e. it won't produce any
> > errors, it would just silently accept it.
> >
> > Also, there's not much error checking there (and to be honest I don't
> > even know how I can do more error checking from within a macro), and
> > if something goes wrong, you'll probably won't even know where exactly
> > error happend, none the less I was extremely amazed at WHAT I could do
> > with Nemerle's macro syntax so I though I'd share it with other people
> > like me, who might really need to use late binding in their programs.
> > =^_^=
> >
> > Now I can say it even more: Nemerle Rocks!
> >
> > P.S.
> > If someone can help me to improve it, help in form of patches would be
> > greatly appreciated :)
> >
> > P.P.S.
> >
> > When I was searching the net on any info about duck typing in Nemerle
> > I occasionaly found this particular statement:
> >
> > http://nemerle.org/irc/nemerle-2006-01-09
> > 13:50 <malekith> the main differences between boo and nemerle is that
> > we do not allow dynamic typing to sneak at without notice, we have
> > better support for metaprogramming (quotations) and compiler written
> > in Nemerle (booc is in C#)
> >
> > After reading it I'm even a little scared if my idea of dynamic typing
> > would be met with knifes and banished like something evil. All I'm
> > trying to do is to give power when one needs it, especially when one
> > *really* needs it. x_x
> >
> > _______________________________________________
> > https://nemerle.org/mailman/listinfo/devel-en
>
>
> _______________________________________________
> https://nemerle.org/mailman/listinfo/devel-en
>


-- 
Kamil Skalski
http://nazgul.omega.pl