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

2 Sep 2010

      2010/9/2 Dave Abrahams <dave@boostpro.com>
...
On Thu, Sep 2, 2010 at 11:57 AM, David Sankel <camior@gmail.com> wrote:
...
Hello all,
I've been working on an alternate bind syntax based on De Bruijn
indices[1].
The syntax is very simple, yet the terms are very powerful.
Here is an example of a function const that takes in an argument c and
returns another function that, for all input, returns c:
//λx.λy.x = λλ1 with De Bruijn indices.
Not according to the page you linked below.  What am I missing?
[1] http://en.wikipedia.org/wiki/De_Bruijn_index
Sorry about that. The wikipedia page uses 1-indexed indices where I'm using
0-indexed indices. So, increment 1 on all my examples to get the wikipedia
syntax.
...
For those of us without time to study up on functional lingo, it would be
interesting to see some examples translated from a C++-ish lambda syntax
(e.g. phoenix, C++0x lambdas, Bind) to your suggestion
A couple bind examples:

bind( f
    , bind( g
          , _1
          )
    )
=>
abs<1>( app( f
           , app( g
                , var<0,0>()
                )
           )
      )

bind( f
    , _1
    , boost::protect( bind( g
                          , 12
                          , _1
                          )
                    )
    )
=>
abs<1>( app( f
           , var<0,0>()
           , abs<1>( app( g
                        , 12
                        , var<0,0>()
                        )
                   )
           )
      )

The reverse direction is not always possible. For example:

abs<1>( app( f
           , var<0,0>()
           , abs<1>( app( g
                        , var<1,0>()
                        , var<0,0>()
                        )
                   )
           )
      )

does not have a corresponding bind.

David

-- 
David Sankel
Sankel Software
www.sankelsoftware.com
585 617 4748 (Office)