Re: [boost] De Bruijn Bind (alternate bind syntax) Interest?

Subject: Re: [boost] De Bruijn Bind (alternate bind syntax) Interest?
From: Stewart, Robert (Robert.Stewart_at_[hidden])
Date: 2010-09-03 07:22:25

David Sankel wrote:
> On Thu, Sep 2, 2010 at 3:41 PM, David Sankel <camior_at_[hidden]> wrote:
> > On Thu, Sep 2, 2010 at 3:21 PM, Dave Abrahams wrote:
>
> >> and how is _1  different from arg<0>?
> >
> > I'm not sure what you mean here. var (or arg if you like)
> > in this library takes two template arguments.
>
> Maybe you're thinking that _1 seems similar to arg<0,0> which
> is true until abstractions (lambdas/binds) get nested.

Shorthand is helpful, so perhaps you could use _1_1, _1_2, _2_1, etc.  (I skipped zero because you were figuring on switching to one-based indexing.)

_1_1 is more readable and succinct than arg<1,1>:

   auto const_ = lam<1>( lam<1>( arg<2,1>() ) );

   auto const_ = lam<1>( lam<1>( _2_1() ) );

and:

   auto flip = lam<1>( lam<2>( app( arg<2,1>()
                                  , arg<1,2>()
                                  , arg<1,1>()
                                  )
                             )
                     );

   auto flip =
      lam<1>(lam<2>(app(_2_1(), _1_2(), _1_1())));

_____
Rob Stewart                           robert.stewart_at_[hidden]
Software Engineer, Core Software      using std::disclaimer;
Susquehanna International Group, LLP  http://www.sig.com

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