local_function/example/impl_tparam_tricks.cpp

72 lines
2.2 KiB
C++

// Copyright (C) 2009-2012 Lorenzo Caminiti
// Distributed under the Boost Software License, Version 1.0
// (see accompanying file LICENSE_1_0.txt or a copy at
// http://www.boost.org/LICENSE_1_0.txt)
// Home at http://www.boost.org/libs/local_function
//[impl_tparam_tricks
#include <boost/detail/lightweight_test.hpp>
#include <vector>
#include <algorithm>
// Casting functor trick.
struct casting_func {
explicit casting_func(void* obj, void (*call)(void*, const int&))
: obj_(obj), call_(call) {}
// Unfortunately, function pointer call is not inlined.
inline void operator()(const int& num) { call_(obj_, num); }
private:
void* obj_;
void (*call_)(void*, const int&);
};
// Virtual functor trick.
struct virtual_func {
struct interface {
// Unfortunately, virtual function call is not inlined.
inline virtual void operator()(const int&) {}
};
explicit virtual_func(interface& func): func_(&func) {}
inline void operator()(const int& num) { (*func_)(num); }
private:
interface* func_;
};
int main(void) {
int sum = 0, factor = 10;
// Local class for local function.
struct local_add : virtual_func::interface {
explicit local_add(int& _sum, const int& _factor)
: sum_(_sum), factor_(_factor) {}
inline void operator()(const int& num) {
body(sum_, factor_, num);
}
inline static void call(void* obj, const int& num) {
local_add* self = static_cast<local_add*>(obj);
self->body(self->sum_, self->factor_, num);
}
private:
int& sum_;
const int& factor_;
inline void body(int& sum, const int& factor, const int& num) {
sum += factor * num;
}
} add_local(sum, factor);
casting_func add_casting(&add_local, &local_add::call);
virtual_func add_virtual(add_local);
std::vector<int> v(10);
std::fill(v.begin(), v.end(), 1);
// std::for_each(v.begin(), v.end(), add_local); // Error but OK on C++11.
std::for_each(v.begin(), v.end(), add_casting); // OK.
std::for_each(v.begin(), v.end(), add_virtual); // OK.
BOOST_TEST(sum == 200);
return boost::report_errors();
}
//]