boost/lambda
2
0
Fork 0
mirror of https://github.com/boostorg/lambda.git synced 2026-01-30 20:02:15 +00:00
Code Issues Projects Releases Wiki Activity

fixed a bug in example code

Browse Source 
[SVN r15576]
This commit is contained in:
Jaakko Järvi
2002-09-30 20:40:07 +00:00
parent 4227c144de
commit 0323ca1876
9 changed files with 53 additions and 50 deletions
Download Patch File Download Diff File Expand all files Collapse all files

25
doc/detail/lambda_doc.xml
View File

@@ -444,7 +444,7 @@ Nevertheless, it is straightforward to provide another function template with th
Next, we create a container of pointers and make them point to the elements in the first container <literal>v</literal>:
<programlisting>
<![CDATA[list<int*> vp(10);
<![CDATA[vector<int*> vp(10);
transform(v.begin(), v.end(), vp.begin(), &_1);]]></programlisting>
The expression <literal><![CDATA[&_1]]></literal> creates a function object for getting the address of each element in <literal>v</literal>.
@@ -1578,13 +1578,7 @@ for_each(a, a+5,
The BLL supports an alternative syntax for control expressions, suggested
by Joel de Guzmann.
By overloading the <literal>operator[]</literal> we can
get a closer resemblance with the built-in control structures.
For example, using this syntax the <literal>if_then</literal> example above
can be written as:
<programlisting>
<![CDATA[for_each(a.begin(), a.end(),
if(_1 % 2 == 0)[ cout << _1 ])]]>
</programlisting>
get a closer resemblance with the built-in control structures:
<programlisting>
<![CDATA[if_(condition)[then_part]
@@ -1594,6 +1588,13 @@ do_[body].while_(condition)
for_(init, condition, increment)[body]]]>
</programlisting>
For example, using this syntax the <literal>if_then</literal> example above
can be written as:
<programlisting>
<![CDATA[for_each(a.begin(), a.end(),
if(_1 % 2 == 0)[ cout << _1 ])]]>
</programlisting>
As more experience is gained, we may end up deprecating one or the other
of these syntaces.
@@ -3029,14 +3030,14 @@ lambda functors; and these wrappers have types that are easy to type out.
For example:
<programlisting>
<![CDATA[boost::function<int, int, int> f = _1 + _2;
boost::function<int&, int&> g = unlambda(_1 += 10);
<![CDATA[boost::function<int(int, int)> f = _1 + _2;
boost::function<int&(int&)> g = (_1 += 10);
int i = 1, j = 2;
f(i); // returns 3
g(i); // sets i to = 11;]]>
</programlisting>
The return and parameter types of the wrapped function object must be written explicilty as template arguments to the wrapper template <literal>boost::function</literal>; even when lambda functors, which otherwise have generic parameters, are wrapped.
The return and parameter types of the wrapped function object must be written explicilty as the template argument to the wrapper template <literal>boost::function</literal>; even when lambda functors, which otherwise have generic parameters, are wrapped.
Wrapping a function object with <literal>boost::function</literal> introduces a performance cost comparable to virtual function dispatch, though virtual functions are not actually used.
Note that storing lambda functors inside <literal>boost::function</literal>
@@ -3054,7 +3055,7 @@ For example:
<programlisting>
<![CDATA[int* sum = new int();
*sum = 0;
boost::function<int&, int> counter = *sum += _1;
boost::function<int&(int)> counter = *sum += _1;
counter(5); // ok, *sum = 5;
delete sum;
counter(3); // error, *sum does not exist anymore]]>