On Saturday, February 26, 2011 11:28:58 PM alfC wrote:

> On Feb 25, 11:57 pm, Thomas Heller <thom.hel...@googlemail.com> wrote:

> > On Saturday, February 26, 2011 08:49:25 AM alfC wrote:

> > > On Jan 31, 5:43 pm, "Hartmut Kaiser" <hartmut.kai...@gmail.com> wrote:

> > > > Hi List,

> > > >

> > > > PhoenixV3 is nearing its completion.

> > > >

> > > > With the port to Boost.Proto we tried to address the outstanding

> > > > issues of the review and would like to announce that

> > > > themini-review will start on February 19th.

> > >

> > > Thank you for the new version of Phoenix-3. I wonder if things like

> > > phoenix-expression matching is now possible as "promised" in this

> > >

> > > thread:

> > >http://lists.boost.org/boost-users/2010/05/59491.php

> >

> > Yes, stuff like this could be indeed made possible.

> > Though, I don't see where phoenix comes into the game in the examples

> > in this thread.

>

> I was doing things like this with Phoenix2 by hacking the internals:

>

> in a function call like this

>

> integral( 'arbitrary phoenix expression' , interval(2., 4.));

>

> I was matching, first that the passed expresion is of the form #1/

> ( phoenix::_1 - #2), if so it checked that #2 is a 'double-type'

> value, then extracted that value and then passed the whole thing to a

> numerical intergrator that handle functions with sigularities at the

> value of #2. If the expression didn't match then a generic integrator

> is called.

Nothing easier than that, no need to hack (more or less) undocumented internals of the library. Every phoenix expression can be matched with proto's grammar matching facilities:

struct singularity :

proto::when<

proto::divides<

proto::_

, proto::minus<

phoenix::expression::argument<1>

, proto::_

>

>

, proto::_value(proto::_right(proto::_right))

>

{};

Match arbitratry expressions with proto::matches ... call the transform to get the singularity, etc.

> Thanks,

> Alfredo