Re: How to convert member function to free function?
On Friday, 18 September 2020 at 18:20:41 UTC, Andrey Zherikov
wrote:
How can I rewrite foo() function as a free-function that won't
cause struct copying?
I found solution:
struct S
{
int i = -1;
this(int n) {i=n;writeln(," ",i,"
",__PRETTY_FUNCTION__);}
this(ref return scope inout S rhs) inout
{i=rhs.i+1;writeln(," ",i," ",__PRETTY_FUNCTION__);}
~this() {writeln(," ",i," ",__PRETTY_FUNCTION__);}
ref auto getRef() return
{
writeln(," ",i," ",__PRETTY_FUNCTION__);
return this;
}
}
ref auto foo(return ref S s)
{
writeln(," ",s.i," ",__PRETTY_FUNCTION__);
return s;
}
void main()
{
S(5).getRef().foo().foo().foo();
}
Output confirms that there is no copying happens:
7FFDE98BDDF0 5 S onlineapp.S.this(int n) ref
7FFDE98BDDF0 5 onlineapp.S.getRef() ref return
7FFDE98BDDF0 5 onlineapp.foo(return ref S s) ref @system
7FFDE98BDDF0 5 onlineapp.foo(return ref S s) ref @system
7FFDE98BDDF0 5 onlineapp.foo(return ref S s) ref @system
7FFDE98BDDF0 5 void onlineapp.S.~this()
Re: How to convert member function to free function?
On Friday, 18 September 2020 at 18:43:38 UTC, H. S. Teoh wrote:
Why can't you return by ref, which would also avoid the copying?
ref S foo(return ref S s) { return s; }
Compiler errors out:
onlineapp.d(9): Error: function onlineapp.foo(return ref S s) is
not callable using argument types (S)
onlineapp.d(9):cannot pass rvalue argument S() of type S
to parameter return ref S s
Re: How to convert member function to free function?
On Fri, Sep 18, 2020 at 06:20:41PM +, Andrey Zherikov via
Digitalmars-d-learn wrote:
> How can I rewrite foo() function as a free-function that won't cause
> struct copying? My simplified code is:
>
> struct S
> {
> ref S foo() return
> {
> return this;
> }
> }
>
> void main()
> {
> S().foo().foo().foo();
> }
>
> If I write it like "auto foo(S s) { return s; }" then statement in
> main() will copy value of S three times and I want to avoid this.
Why can't you return by ref, which would also avoid the copying?
ref S foo(return ref S s) { return s; }
T
--
Let's not fight disease by killing the patient. -- Sean 'Shaleh' Perry
How to convert member function to free function?
How can I rewrite foo() function as a free-function that won't
cause struct copying? My simplified code is:
struct S
{
ref S foo() return
{
return this;
}
}
void main()
{
S().foo().foo().foo();
}
If I write it like "auto foo(S s) { return s; }" then statement
in main() will copy value of S three times and I want to avoid
this.
