Re: Lambda Expression + RAII = The landscape of exception-safe programming will change in C++09!
On Sep 24, 6:42 pm, pongba <pon...@gmail.com> wrote:
Exception-safe Programming is hard, but a scope(exit) facility like
that of D language can ease the task. Now it is difficult in C++03 to
implement a easy to use one (http://194.6.223.221/~nasonov/
scope_exit-0.04/libs/scope_exit/doc/html/index.html).
With C++09 coming, we can except that a much more elegant solution is
on the horizon!
Check the code below:
class ScopeExit
{
public:
ScopeExit(tr1::function<void()> func) : func_(func) { }
~ScopeExit() { func_(); }
private:
tr1::function<void()> func_;
};
#define BOOST_SCOPE_EXIT(expr) \
ScopeExit scope_exit_##__LINE__(expr)
The cost of using tr1::function (to be std::function in C++09) can be
avoided:
template<class F>
class ScopeExit
{
public:
ScopeExit(F func) : func_(func) { }
~ScopeExit() { func_(); }
private:
F func_;
};
template<class F>
ScopeExit<F> make_ScopeExit(F func)
{
return ScopeExit<F>(func);
}
#define BOOST_SCOPE_EXIT(expr) \
auto scope_exit_##__LINE__(make_ScopeExit(expr))
// use case
void f()
{
bool commit = false;
account1.draw(10);
BOOST_SCOPE_EXIT((
<&>(){
if(!commit)
account1.deposit(10);
}
)); // lambda expression - see proposal N2413
account2.deposit(10);
commit = true;
}
Usage unchanged.
Yechezkel Mett
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