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Home » Extra libraries, Code snippets, applications etc. » C++ language problems and code snippets » Make THISFN simpler and more powerful (by taking advantage of some new c++ feature)

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Re: Make THISFN simpler and more powerful [message #59157 is a reply to message #59156]

Thu, 10 November 2022 21:41

Lance is currently offline

Lance
Messages: 656
Registered: March 2007

Contributor

Some failed attempts.

template <class T>
concept UppMoveable = requires (T t){
    Upp::Vector<T> v;
    v.Add(t);
};

This will fail in compilation with a strange error message.

Turns out you cannot do variable declaration in a requires-expression.

Something like this

template <class T>
concept UppMoveable = requires (T t, Upp::Vector<T> v){
    v.Add(t);
};

compiles fine but doesn't give desired results. Compiler only check if expressions inside a requires-expression are well-formed. Evaluation doesn't take place.

So this won't work. Back to old conclusion: we need a way to check is a class T is declared/defined with something like

class MyString : public Moveable<MyString, optionalB>{...};

to determine if it can be placed in a Upp::Vector.

Here are some well written articles about concepts and requires-expression.

C++20 Concepts - a Quick Introduction

Requires-expression

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[Message index]

		Make THISFN simpler and more powerful By: Lance on Tue, 18 October 2022 21:08
		Re: Make THISFN simpler and more powerful By: Lance on Thu, 10 November 2022 00:32
		Re: Make THISFN simpler and more powerful By: Oblivion on Thu, 10 November 2022 06:29
		Re: Make THISFN simpler and more powerful By: Lance on Thu, 10 November 2022 12:52
		Re: Make THISFN simpler and more powerful By: Lance on Thu, 10 November 2022 21:41
		Re: Make THISFN simpler and more powerful By: Lance on Fri, 11 November 2022 02:50
		Re: Make THISFN simpler and more powerful By: Lance on Tue, 08 October 2024 18:38
		Re: Make THISFN simpler and more powerful By: Lance on Tue, 08 October 2024 18:42
		Re: Make THISFN simpler and more powerful By: Didier on Tue, 08 October 2024 19:25
		Re: Make THISFN simpler and more powerful By: Lance on Tue, 08 October 2024 20:01
		Re: Make THISFN simpler and more powerful By: Lance on Wed, 09 October 2024 05:59
		Re: Make THISFN simpler and more powerful By: Lance on Wed, 09 October 2024 16:09
		Re: Make THISFN simpler and more powerful By: Lance on Wed, 09 October 2024 16:17
		Re: Make THISFN simpler and more powerful By: Didier on Wed, 09 October 2024 19:32
		Re: Make THISFN simpler and more powerful By: Lance on Thu, 10 October 2024 14:01
		Re: Make THISFN simpler and more powerful By: Lance on Thu, 10 October 2024 14:06
		Re: Make THISFN simpler and more powerful By: Lance on Tue, 05 November 2024 02:25
		Re: Make THISFN simpler and more powerful By: Lance on Tue, 05 November 2024 02:33
		Re: Make THISFN simpler and more powerful By: Lance on Thu, 07 November 2024 00:49
		Re: Make THISFN simpler and more powerful By: Lance on Fri, 29 November 2024 02:30

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