Update of /cvsroot/boost/boost/libs/parameter/doc
In directory sc8-pr-cvs3.sourceforge.net:/tmp/cvs-serv6113
Modified Files:
index.rst
Log Message:
Fixed examples and removed use of boost::lambda.
Index: index.rst
===================================================================
RCS file: /cvsroot/boost/boost/libs/parameter/doc/index.rst,v
retrieving revision 1.49
retrieving revision 1.50
diff -u -d -r1.49 -r1.50
--- index.rst 3 Jan 2007 16:42:27 -0000 1.49
+++ index.rst 1 May 2007 14:43:47 -0000 1.50
@@ -1067,8 +1067,8 @@
.. parsed-literal::
- def("f", f, **some_policies**, **"Documentation for f"**);
- def("f", f, **"Documentation for f"**, **some_policies**);
+ def("f", &f, **some_policies**, **"Documentation for f"**);
+ def("f", &f, **"Documentation for f"**, **some_policies**);
.. @example.prepend('''
int main()
@@ -1081,7 +1081,7 @@
.. parsed-literal::
def(
- "f", f
+ "f", &f
, **_policies = some_policies**, "Documentation for f");
.. @example.append('}')
@@ -1114,7 +1114,8 @@
};
.. @example.prepend('''
- #include <boost/parameter.hpp>''')
+ #include <boost/parameter.hpp>
+ #include <iostream>''')
.. @test('compile')
@@ -1701,7 +1702,10 @@
, optional<tag::\ index, is_convertible<_,int> >
> spec;
- int z0 = print_name_and_index( **spec(**\ "sam", 12\ **)** );
+ char const sam[] = "sam";
+ int twelve = 12;
+
+ int z0 = print_name_and_index( **spec(**\ sam, twelve\ **)** );
int z1 = print_name_and_index(
**spec(**\ _index=12, _name="sam"\ **)**
@@ -1720,6 +1724,11 @@
.. @test('run', howmany='all')
+Note that because of the `forwarding problem`_,
``parameter::parameters::operator()``
+can't accept non-const rvalues.
+
+.. _`forwarding problem`:
http://std.dkuug.dk/jtc1/sc22/wg21/docs/papers/2002/n1385.htm
+
Extracting Parameter Types
==========================
@@ -1770,7 +1779,9 @@
BOOST_PARAMETER_NAME(index)
template <class ArgumentPack>
- typename parameter::binding<ArgumentPack, tag::index, int>::type
+ typename remove_reference<
+ typename parameter::binding<ArgumentPack, tag::index, int>::type
+ >::type
twice_index(ArgumentPack const& args)
{
return 2 * args[_index|42];
@@ -1778,21 +1789,44 @@
int six = twice_index(_index = 3);
-.. TODO: binding<> returns a reference. We should use value_type<> here.
-
.. @example.prepend('''
#include <boost/parameter.hpp>
+ #include <boost/type_traits/remove_reference.hpp>
#include <cassert>
- namespace parameter = boost::parameter;''')
+ namespace parameter = boost::parameter;
+ using boost::remove_reference;''')
+
+Note that the ``remove_reference< ⦠>`` dance is necessary because
+``binding< ⦠>`` will return a reference type when the argument
+is bound in the argument pack. If we don't strip the reference we
+end up returning a reference to the temporary created in the ``2 * â¦``
+expression. A convenient shortcut would be to use the ``value_type< ⦠>``
+metafunction:
+
+.. parsed-literal::
+
+ template <class ArgumentPack>
+ typename **parameter::value_type<ArgumentPack, tag::index, int>**::type
+ twice_index(ArgumentPack const& args)
+ {
+ return 2 * args[_index|42];
+ }
+
+.. @example.wrap('namespace with_value_type {', '''
+ int six = twice_index(_index = 3);
+ }''')
+
+.. TODO: binding<> returns a reference. We should use value_type<> here.
.. @example.append('''
int main()
{
assert(six == 6);
+ assert(with_value_type::six == 6);
}''')
-.. @test('run')
+.. @test('run', howmany='all')
__ binding_intro_
@@ -1837,21 +1871,31 @@
In the example above, the string ``"hello, world"`` is constructed
despite the fact that the user passed us a value for ``s3``. To
remedy that, we can compute the default value *lazily* (that is,
-only on demand), by combining the logical-or (â``||``â) operator
-with a function object built by the Boost Lambda_ library: [#bind]_
+only on demand), by using ``boost::bind()`` to create a function
+object.
+
+.. danielw: I'm leaving the text below in the source, because we might
+.. want to change back to it after 1.34, and if I remove it now we
+.. might forget about it.
+
+.. by combining the logical-or (â``||``â) operator
+.. with a function object built by the Boost Lambda_ library: [#bind]_
.. parsed-literal::
- namespace lambda = boost::lambda;
+ using boost::bind;
+ using boost::ref;
typename parameter::binding<
ArgumentPack, tag::s3, std::string
- >::type s3 = args[_s3 **|| (lambda::var(s1)+lambda::var(s2))** ];
+ >::type s3 = args[_s3 **|| bind(std::plus<std::string>(), ref(s1),
ref(s2))** ];
.. @example.prepend('''
- #include <boost/lambda/lambda.hpp>
+ #include <boost/bind.hpp>
+ #include <boost/ref.hpp>
#include <boost/parameter.hpp>
#include <string>
+ #include <functional>
namespace parameter = boost::parameter;
@@ -1876,7 +1920,7 @@
.. @test('run')
-.. _Lambda: ../../../lambda/index.html
+.. .. _Lambda: ../../../lambda/index.html
.. sidebar:: Mnemonics
@@ -1886,10 +1930,15 @@
Similarly, in ``color_map[param||f]``, ``f`` is only invoked if
no ``color_map`` argument was supplied.
-The expression ``lambda::var(s1)+lambda::var(s2)`` yields a
-*function object* that, when invoked, adds the two strings
-together. That function will only be invoked if no ``s3`` argument
-is supplied by the caller.
+The expression ``bind(std::plus<std::string>(), ref(s1), ref(s2))`` yields
+a *function object* that, when invoked, adds the two strings together.
+That function will only be invoked if no ``s3`` argument is supplied by
+the caller.
+
+.. The expression ``lambda::var(s1)+lambda::var(s2)`` yields a
+.. *function object* that, when invoked, adds the two strings
+.. together. That function will only be invoked if no ``s3`` argument
+.. is supplied by the caller.
================
Best Practices
@@ -2251,17 +2300,17 @@
.. _`ConceptC++`: http://www.generic-programming.org/software/ConceptGCC/
-.. [#bind] The Lambda library is known not to work on `some
- less-conformant compilers`__. When using one of those you could
- use `Boost.Bind`_ to generate the function object::
+.. .. [#bind] The Lambda library is known not to work on `some
+.. less-conformant compilers`__. When using one of those you could
+.. use `Boost.Bind`_ to generate the function object::
- boost::bind(std::plus<std::string>(),s1,s2)
+.. boost::bind(std::plus<std::string>(),s1,s2)
.. [#is_keyword_expression] Here we're assuming there's a predicate
metafunction ``is_keyword_expression`` that can be used to
identify models of Boost.Python's KeywordExpression concept.
-__ http://www.boost.org/regression/release/user/lambda.html
+.. .. __ http://www.boost.org/regression/release/user/lambda.html
.. _Boost.Bind: ../../../bind/index.html
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