From: Corwin Joy (cjoy_at_[hidden])
Date: 2001-07-19 02:39:49
One other point. One also gets semi-scripting capabilities from any_ccast
any a(double(2.5)), b(int(3));
any c= any_ccast<double>(a) + any_ccast<double>(b);
assigns c a type of double with a value of 5.5
----- Original Message -----
From: "Corwin Joy" <cjoy_at_[hidden]>
Sent: Thursday, July 19, 2001 2:10 AM
Subject: [boost] Proposal: converting casts for 'any'
> I have uploaded to the boost website a set of files for registering and
> performing conversion casts with an 'any' object into the folder
> This can be done without making modifications to the current 'any'
> structure. The syntax for this cast looks like this:
> any_ccast ('any' converting cast)
> template<typename ValueType>
> ValueType any_ccast(const any & operand);
> Custom keyword cast for extracting a value of a given type from an any
> a possible conversion to get the requested type. If the conversion from
> type held by any to the requested value type is allowed then this returns
> copy of the extracted result if successful, otherwise a bad_cast exception
> is thrown. any_ccast is normally used when you don't know the exact type
> held by an 'any' variable and you want to request a (possibly) converting
> cast to a given format.
> any a(double(3.5));
> // These will invoke boost::numeric_cast
> cout << any_ccast<int>(a) << endl; // cast out 'any' contents to an int
> cout << any_ccast<float>(a) << endl; // cast out 'any' contents to a float
> // This will use boost::lexical_cast
> cout << any_ccast<string>(a) << endl; // cast out 'any' contents to string
> similarly, one can write:
> any a(string("12345"));
> cout << any_ccast<int>(a) << endl; // lexical cast to an int
> For more examples see the documentation and tests in the uploaded folder.
> Users can also add their own classes and user defined casts as shown in
> cast_registry constructor in any_ccast.cpp. Essentially the syntax is
> g_cast_registry.add_cast_fn(id_for_target_type, id_for_source_type,
> see any_ccast.cpp for details.
> Info: http://www.boost.org Unsubscribe:
> Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/
Boost list run by bdawes at acm.org, gregod at cs.rpi.edu, cpdaniel at pacbell.net, john at johnmaddock.co.uk