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GO's defer-like implementation for CPP
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/* | |
* Copyright (c) 2020-present Daniel Trugman | |
* | |
* Permission is hereby granted, free of charge, to any person obtaining a copy | |
* of this software and associated documentation files (the "Software"), to deal | |
* in the Software without restriction, including without limitation the rights | |
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell | |
* copies of the Software, and to permit persons to whom the Software is | |
* furnished to do so, subject to the following conditions: | |
* | |
* The above copyright notice and this permission notice shall be included in all | |
* copies or substantial portions of the Software. | |
* | |
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR | |
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, | |
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE | |
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER | |
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, | |
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE | |
* SOFTWARE. | |
*/ | |
#include <functional> | |
#define var_defer__(x) defer__ ## x | |
#define var_defer_(x) var_defer__(x) | |
#define ref_defer(ops) defer var_defer_(__COUNTER__)([&]{ ops; }) // Capture all by ref | |
#define val_defer(ops) defer var_defer_(__COUNTER__)([=]{ ops; }) // Capture all by val | |
#define none_defer(ops) defer var_defer_(__COUNTER__)([ ]{ ops; }) // Capture nothing | |
class defer | |
{ | |
public: | |
using action = std::function<void(void)>; | |
public: | |
defer(const action& act) | |
: _action(act) {} | |
defer(action&& act) | |
: _action(std::move(act)) {} | |
defer(const defer& act) = delete; | |
defer& operator=(const defer& act) = delete; | |
defer(defer&& act) = delete; | |
defer& operator=(defer&& act) = delete; | |
~defer() | |
{ | |
_action(); | |
} | |
private: | |
action _action; | |
}; |
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#include <iostream> | |
#include "defer.hpp" | |
int main() | |
{ | |
std::string message("goodbye"); | |
// Usage without macro wraps | |
defer defer_it([&message]{ std::cout << message << std::endl; }); | |
// Use macro that captures nothing | |
none_defer(std::cout << "msg hard-coded" << std::endl); | |
// Use macro that captures all members by value | |
val_defer(std::cout << "msg by val: " << message << std::endl); | |
// Use macro that captures all members by reference | |
ref_defer(std::cout << "msg by ref: " << message << std::endl); | |
message += " friend"; | |
return 0; | |
} |
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