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Questions tagged [policy-based-design]

56 questions
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Mechanics of multiple inheritance compared to templates wrt building flexible designs

This is a narrower version of the question put on hold due to being too broad. On pages 6-7 of Modern C++ Design, Andrei Alexandrescu lists three ways in which the multiple inheritance is weaker than templates with respect to building flexible…
AlwaysLearning
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Policy based design and defaults

Hard to come up with a good title for this question. What I really need is to be able to provide template parameters with different number of arguments in place of a single parameter. Doesn't make a lot of sense so I'll go over the…
Edward Strange
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C++ Copy/Move constructor in policy based design

While exploring Policy Based Design pattern in C++, I stumbled upon one problem which I could not find a solution to: How do you write copy and move constructors for policy based classes in a generic way without referring to member variables inside…
Pranav
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Java Policy-Based Design

I have a while loop, and the user should be able to decide when the loop stops. After x seconds, after x loops, ... This problem should be implemented according to policy-based design. I know how to do this in C++ but can't get it to work in…
Niel
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Policy based design decisions

I have a class called Device that accepts two policies as far as I can see: StatePolicy and BehaviorPolicy. The StatePolicy holds and manages the state of the device. The BehaviorPolicy wraps the device driver that is written in C or C++. Now I have…
the_drow
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Converting a compile-time C callbacks to compile-time C++ callbacks

I'm converting a C codebase to C++ for an embedded device (ESP32). One thing that's repeating in the current code is a way of declaring "callbacks" to C modules and implement them in the "user" module. For example, the current API for a Button…
galah92
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C++ Template Meta Programming: Inheritance from template template parameter

#include template struct mutable_storage {}; template < template class storage_t, typename T2 = void, typename is_allocated =…
Lourens Dijkstra
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Use of unique_ptr in classes with protected destructors

I am studying policy based design from Modern C++ Design, and I have got stuck in a simple example below, where I was trying to use a std::vector of std::unique_ptrs in my templated policy class: #include #include template
enanone
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C++ Policy Based Design

What I do not understand in the Alexandrescu policy based design is the creation of new types without anything in common where, in my opinion, there is still a lot in common that should be represented somehow. For example, std::string and…
nyarlathotep108
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Policy classes with differing interfaces

Suppose an algorithm that has a policy FooPolicy. Policy classes that implement this policy feature a static member function foo, but, for some of them, foo takes an int argument, while for others it does not. I am trying to enable the use of these…
AlwaysLearning
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Are named template arguments in the newest Standard or implemented in a contemporary compiler?

Named template arguments would arguably be a very important feature in C++. Namely, given a class template that has many template parameters with default arguments, this feature would allow the user to provide arguments for an arbitrary subset of…
AlwaysLearning
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Policy conversion operator vs private destructor in policy-based class

In Modern C++ Design: Generic Programming and Design Patterns Applied Andrei Alexandrescu advocates for making the policies' destructor protected: Because the destructor is protected, only derived classes can destroy policy objects, so it's…
tsuki
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Run-time polymorphism design and strategies with CRTP

In my work I have a lot of loops with many inner function calls; performance is critical here, and the overhead of virtual function calls is unacceptable, so I try to avoid dynamic polymorphism by using CRTP, like so: template struct…
Aurelius
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Ambiguous inheritance in policy-based design

I have a host class, which takes two policies, sayhello and talk. The policy talk is a class template, which itself takes e.g. sayhello. The problem is that sayhello::saySomething is ambiguous in host2 (i tried to solve this diamond problem with…
the_ducky
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How to realize the policy based design with class mixins?

I know how i can realize a implementation of a class with the policy based design pattern from c++ with Interfaces. I don't know how to do the same with class mixin's. This would be useful if you want to squeze the last performance out of your code…
Quonux
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