220 26785 <4b8b5bd1-d8e2-4f70-bb83-96cc3dd519a9@isocpp.org> article Path: news.gmane.org!not-for-mail From: ezmagician@gmail.com Newsgroups: gmane.comp.lang.c++.isocpp.proposals Subject: `pure` virt-specifier-seq to denote pure virtual functions. 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It would follow the same rules as the `override` and `final` specifiers. This syntax would also allow a clear, simple syntax for in-class definitions. struct A { // In class pure virtual function definitions. // Follows same syntax as override and final specifiers, which are also // used to describe/enforce properties of virtual functions. virtual void foo() pure; virtual void bar() pure; // Allows for function definitions in the class declaration using the same // syntax as the override and final specifiers without the strange look of // previously suggested syntax of the form: void func() = 0 { }. virtual void ~A() pure = default; // Current syntax for denoting a pure function is strange. // This syntax is not used anywhere else in C++ (to my knowledge). // virtual void ~A() = 0; // Compiler error message seems to imply that a pure virtual function // cannot have a definition: "error: pure-specifier on function-definition" // virtual void bar() = 0 { }; }; // The current way to define a pure virtual function by overloading the function // outside the class declaration is non-intuitive. // Danger of multiple definition errors if not inlined in a header. // inline void A::A~() = default; struct B : A { void foo() override final { } // pure specifier does not conflict with other virtual specifiers, although // the use of a pure-final function may be questionable. void bar() override pure; }; -- You received this message because you are subscribed to the Google Groups "ISO C++ Standard - Future Proposals" group. To unsubscribe from this group and stop receiving emails from it, send an email to std-proposals+unsubscribe@isocpp.org. To post to this group, send email to std-proposals@isocpp.org. To view this discussion on the web visit https://groups.google.com/a/isocpp.org/d/msgid/std-proposals/4b8b5bd1-d8e2-4f70-bb83-96cc3dd519a9%40isocpp.org. ------=_Part_502_599407637.1468272719349 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable
What are your thoughts on adding a new virt-specifier= -seq specifying that a function is pure virtual?

It would follow the same rules as the `override` and `final` specifiers.=
This syntax would also allow a clear, simple syntax for in-class= definitions.

struct A {
// =C2=A0In class pure virtual fun= ction definitions.
// =C2=A0Follows same syntax as override and final specifiers, which are = also
// =C2=A0use= d to describe/enforce properties of virtual functions.
=C2=A0 =C2=A0 virtual void foo() pure;
=C2=A0 =C2=A0 virtual void bar= ()<= span style=3D"color: #000;" class=3D"styled-by-prettify"> pure;

// =C2=A0Allows for function defin= itions in the class declaration using the same
// =C2=A0syntax as the override and final spe= cifiers without the strange look of
// =C2=A0previously suggested syntax of the form: void f= unc() =3D 0 { }.
=C2=A0 =C2=A0 virtual void ~A() pure =3D default;

// =C2=A0Current syntax for denoting a pure function is strange.
// =C2=A0This syntax is n= ot used anywhere else in C++ (to my knowledge).
// =C2=A0virtual void ~A() =3D 0;

// =C2=A0Compiler error= message seems to imply that a pure virtual function
// =C2=A0cannot have a definition: &quo= t;error: pure-specifier on function-definition"
// =C2=A0virtual void bar() =3D 0 { };<= /span>
= };

// The current way to defin= e a pure virtual function by overloading the function
// outside the class declaration is no= n-intuitive.
// = Danger of multiple definition errors if not inlined in a header.
// inline void A::A~() =3D = default;
stru= ct B : A {
=C2=A0 =C2=A0 void foo() override final = { }

// =C2=A0pure specifier does not confli= ct with other virtual specifiers, although
// =C2=A0the use of a pure-final function may be = questionable.
=C2=A0 =C2=A0 void bar(= ) <= span style=3D"color: #008;" class=3D"styled-by-prettify">override pure;
};


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