diff --git a/index.html b/index.html index c53b817..b1b9399 100644 --- a/index.html +++ b/index.html @@ -5,6 +5,10 @@ Automatic redirection failed, please go to bind.html or -mem_fn.html. +mem_fn.html. 
+

© Copyright Beman Dawes, 2001

+

Distributed under the Boost Software License, Version 1.0. (See accompanying +file LICENSE_1_0.txt or copy +at www.boost.org/LICENSE_1_0.txt)

- + \ No newline at end of file diff --git a/mem_fn.html b/mem_fn.html index 5cc89f2..f04a667 100644 --- a/mem_fn.html +++ b/mem_fn.html @@ -1,407 +1,14 @@ - - - Boost: mem_fn.hpp documentation - - - - - - - - - - - -
boost.png (6897 bytes) - -

mem_fn.hpp

-
 
-

Contents

-

Purpose

-

Frequently Asked Questions

-

Can mem_fn be used instead of the - standard std::mem_fun[_ref] adaptors?

-

Should I replace every occurence of std::mem_fun[_ref] - with mem_fn in my existing code?

-

Does mem_fn work with COM methods?

-

Why isn't BOOST_MEM_FN_ENABLE_STDCALL - defined automatically?

-

Interface

-

Synopsis

-

Common requirements

-

get_pointer

-

mem_fn

-

Implementation

-

Files

-

Dependencies

-

Number of Arguments

-

"__stdcall", "__cdecl" and - "__fastcall" Support

-

Acknowledgements

-

Purpose

-

- boost::mem_fn is a generalization of the standard functions std::mem_fun - and std::mem_fun_ref. It supports member function pointers with more - than one argument, and the returned function object can take a pointer, a - reference, or a smart pointer to an object instance as its first argument. mem_fn - also supports pointers to data members by treating them as functions taking no - arguments and returning a (const) reference to the member. -

-

- The purpose of mem_fn is twofold. First, it allows users to invoke a - member function on a container with the familiar -

- 
-    std::for_each(v.begin(), v.end(), boost::mem_fn(&Shape::draw));
-
-

- syntax, even when the container stores smart pointers. -

-

- Second, it can be used as a building block by library developers that want to - treat a pointer to member function as a function object. A library might define - an enhanced for_each algorithm with an overload of the form: -

- 
-template<class It, class R, class T> void for_each(It first, It last, R (T::*pmf) ())
-{
-    std::for_each(first, last, boost::mem_fn(pmf));
-}
-
-

- that will allow the convenient syntax: -

- 
-    for_each(v.begin(), v.end(), &Shape::draw);
-
-

- When documenting the feature, the library author will simply state: -

-

template<class It, class R, class T> void - for_each(It first, It last, R (T::*pmf) ());

-

- Effects: equivalent to std::for_each(first, last, boost::mem_fn(pmf)); -

-

- where boost::mem_fn can be a link to this page. See the - documentation of bind for an example. -

-

- mem_fn takes one argument, a pointer to a member, and returns a function - object suitable for use with standard or user-defined algorithms: -

- 
-struct X
-{
-    void f();
-};
-
-void g(std::vector<X> & v)
-{
-    std::for_each(v.begin(), v.end(), boost::mem_fn(&X::f));
-};
-
-void h(std::vector<X *> const & v)
-{
-    std::for_each(v.begin(), v.end(), boost::mem_fn(&X::f));
-};
-
-void k(std::vector<boost::shared_ptr<X> > const & v)
-{
-    std::for_each(v.begin(), v.end(), boost::mem_fn(&X::f));
-};
-
-

- The returned function object takes the same arguments as the input member - function plus a "flexible" first argument that represents the object instance. -

-

- When the function object is invoked with a first argument x that is - neither a pointer nor a reference to the appropriate class (X in the - example above), it uses get_pointer(x) to obtain a pointer from x. - Library authors can "register" their smart pointer classes by supplying an - appropriate get_pointer overload, allowing mem_fn to recognize - and support them. -

-

- [Note: get_pointer is not restricted to return a pointer. Any object - that can be used in a member function call expression (x->*pmf)(...) - will work.] -

-

- [Note: the library uses an unqualified call to get_pointer. Therefore, - it will find, through argument-dependent lookup, get_pointer overloads - that are defined in the same namespace as the corresponding smart pointer - class, in addition to any boost::get_pointer overloads.] -

-

- All function objects returned by mem_fn expose a result_type typedef - that represents the return type of the member function. For data members, result_type - is defined as the type of the member. -

-

Frequently Asked Questions

-

Can mem_fn be used instead of the standard std::mem_fun[_ref] - adaptors?

-

- Yes. For simple uses, mem_fn provides additional functionality that the - standard adaptors do not. Complicated expressions that use std::bind1st, std::bind2nd - or Boost.Compose along with the - standard adaptors can be rewritten using boost::bind - that automatically takes advantage of mem_fn. -

-

Should I replace every occurence of std::mem_fun[_ref] with mem_fn - in my existing code?

-

- No, unless you have good reasons to do so. mem_fn is not 100% compatible - with the standard adaptors, although it comes pretty close. In particular, mem_fn - does not return objects of type std::[const_]mem_fun[1][_ref]_t, as the - standard adaptors do, and it is not possible to fully describe the type of the - first argument using the standard argument_type and first_argument_type - nested typedefs. Libraries that need adaptable function objects in order to - function might not like mem_fn. -

-

Does mem_fn work with COM methods?

-

- Yes, if you #define BOOST_MEM_FN_ENABLE_STDCALL. -

-

Why isn't BOOST_MEM_FN_ENABLE_STDCALL defined automatically?

-

- Non-portable extensions, in general, should default to off to prevent vendor - lock-in. Had BOOST_MEM_FN_ENABLE_STDCALL been defined automatically, you could - have accidentally taken advantage of it without realizing that your code is, - perhaps, no longer portable. In addition, it is possible for the default - calling convention to be __stdcall, in which case enabling __stdcall support - will result in duplicate definitions. -

-

Interface

-

Synopsis

- 
-namespace boost
-{
-
-template<class T> T * get_pointer(T * p);
-
-template<class R, class T> unspecified-1 mem_fn(R (T::*pmf) ());
-
-template<class R, class T> unspecified-2 mem_fn(R (T::*pmf) () const);
-
-template<class R, class T> unspecified-2-1 mem_fn(R T::*pm);
-
-template<class R, class T, class A1> unspecified-3 mem_fn(R (T::*pmf) (A1));
-
-template<class R, class T, class A1> unspecified-4 mem_fn(R (T::*pmf) (A1) const);
-
-template<class R, class T, class A1, class A2> unspecified-5 mem_fn(R (T::*pmf) (A1, A2));
-
-template<class R, class T, class A1, class A2> unspecified-6 mem_fn(R (T::*pmf) (A1, A2) const);
-
-// implementation defined number of additional overloads for more arguments
-
-}
-
-

Common requirements

-

- All unspecified-N types mentioned in the Synopsis are CopyConstructible - and Assignable. Their copy constructors and assignment operators do not - throw exceptions. unspecified-N::result_type is defined as the - return type of the member function pointer passed as an argument to mem_fn - (R in the Synopsis.) unspecified-2-1::result_type is - defined as R. -

-

get_pointer

-

template<class T> T * get_pointer(T * p)

-
-

- Returns: p. -

-

- Throws: Nothing. -

-
-

mem_fn

-

template<class R, class T> unspecified-1 mem_fn(R - (T::*pmf) ())

-
-

- Returns: a function object f such that the expression f(t) - is equivalent to (t.*pmf)() when t is an l-value of type T - or derived, (get_pointer(t)->*pmf)() otherwise. -

-

- Throws: Nothing. -

-
-

template<class R, class T> unspecified-2 mem_fn(R - (T::*pmf) () const)

-
-

- Returns: a function object f such that the expression f(t) - is equivalent to (t.*pmf)() when t is of type T - [const] or derived, (get_pointer(t)->*pmf)() - otherwise. -

-

- Throws: Nothing. -

-
-

template<class R, class T> unspecified-2-1 mem_fn(R - T::*pm)

-
-

- Returns: a function object f such that the expression f(t) - is equivalent to t.*pm when t is of type T [const] - or derived, get_pointer(t)->*pm otherwise. -

-

- Throws: Nothing. -

-
-

template<class R, class T, class A1> unspecified-3 mem_fn(R - (T::*pmf) (A1))

-
-

- Returns: a function object f such that the expression f(t, a1) - is equivalent to (t.*pmf)(a1) when t is an l-value of type T - or derived, (get_pointer(t)->*pmf)(a1) otherwise. -

-

- Throws: Nothing. -

-
-

template<class R, class T, class A1> unspecified-4 mem_fn(R - (T::*pmf) (A1) const)

-
-

- Returns: a function object f such that the expression f(t, a1) - is equivalent to (t.*pmf)(a1) when t is of type T - [const] or derived, (get_pointer(t)->*pmf)(a1) - otherwise. -

-

- Throws: Nothing. -

-
-

template<class R, class T, class A1, class A2> unspecified-5 - mem_fn(R (T::*pmf) (A1, A2))

-
-

- Returns: a function object f such that the expression f(t, a1, a2) - is equivalent to (t.*pmf)(a1, a2) when t is an l-value of type - T or derived, (get_pointer(t)->*pmf)(a1, a2) otherwise. -

-

- Throws: Nothing. -

-
-

template<class R, class T, class A1, class A2> unspecified-6 - mem_fn(R (T::*pmf) (A1, A2) const)

-
-

- Returns: a function object f such that the expression f(t, a1, a2) - is equivalent to (t.*pmf)(a1, a2) when t is of type T - [const] or derived, (get_pointer(t)->*pmf)(a1, a2) otherwise. -

-

- Throws: Nothing. -

-
-

Implementation

-

Files

- -

Dependencies

- -

Number of Arguments

-

- This implementation supports member functions with up to eight arguments. This - is not an inherent limitation of the design, but an implementation detail. -

-

"__stdcall", "__cdecl" and "__fastcall" Support

-

- Some platforms allow several types of member functions that differ by their calling - convention (the rules by which the function is invoked: how are - arguments passed, how is the return value handled, and who cleans up the stack - - if any.) -

-

- For example, Windows API functions and COM interface member functions use a - calling convention known as __stdcall. Borland VCL components use __fastcall. - UDK, the component model of OpenOffice.org, uses __cdecl. -

-

- To use mem_fn with __stdcall member functions, #define the - macro BOOST_MEM_FN_ENABLE_STDCALL before including, directly or - indirectly, <boost/mem_fn.hpp>. -

-

To use mem_fn with __fastcall member functions, #define the - macro BOOST_MEM_FN_ENABLE_FASTCALL before including <boost/mem_fn.hpp>. -

-

To use mem_fn with __cdecl member functions, #define the - macro BOOST_MEM_FN_ENABLE_CDECL before including <boost/mem_fn.hpp>. -

-

It is best to define these macros in the project options, via -D on the - command line, or as the first line in the translation unit (.cpp file) where - mem_fn is used. Not following this rule can lead to obscure errors - when a header includes mem_fn.hpp before the macro has been defined.

-

[Note: this is a non-portable extension. It is not part of the interface.] -

-

- [Note: Some compilers provide only minimal support for the __stdcall keyword.] -

-

Acknowledgements

-

- Rene Jager's initial suggestion of using traits classes to make mem_fn adapt - to user-defined smart pointers inspired the get_pointer-based design. -

-

- Numerous improvements were suggested during the formal review period by Richard - Crossley, Jens Maurer, Ed Brey, and others. Review manager was Darin Adler. -

-

- Steve Anichini pointed out that COM interfaces use __stdcall. -

-

- Dave Abrahams modified bind and mem_fn to support void returns on - deficient compilers. -

-

Daniel Boelzle pointed out that UDK uses __cdecl.
-
-
- Copyright © 2001, 2002 by Peter Dimov and Multi Media Ltd. Copyright - 2003-2005 Peter Dimov. Permission to copy, use, modify, sell and distribute - this document is granted provided this copyright notice appears in all copies. - This document is provided "as is" without express or implied warranty, and with - no claim as to its suitability for any purpose.

- - + + + + +Automatic redirection failed, please go to +../bind/mem_fn.html. 
+

© Copyright Beman Dawes, 2001

+

Distributed under the Boost Software License, Version 1.0. (See accompanying +file LICENSE_1_0.txt or copy +at www.boost.org/LICENSE_1_0.txt)

+

 

+ + \ No newline at end of file