digitalmars.D.learn - does alias this work correctly?
- Zhenya (30/30) Jan 13 2013 Hi!
- Maxim Fomin (10/40) Jan 13 2013 According to spec http://dlang.org/class.html#AliasThis undefined
- Zhenya (4/45) Jan 13 2013 I just want very much avoid renaming function,it's principle for
- Jonathan M Davis (5/20) Jan 13 2013 It functions exactly like it's supposed to. As Maxim said, undefined loo...
- Zhenya (3/29) Jan 14 2013 Now it's clear for me,thank you.
- Zhenya (28/54) Jan 14 2013 import std.stdio;
- Jonathan M Davis (9/38) Jan 14 2013 I honestly have no idea how opDispatch and alias this are supposed to
- Zhenya (5/49) Jan 14 2013 :( If compiler tried alias this before opDispatch all would be OK.
- Andrey (21/24) Jan 13 2013 I think that the main overall principle here is that is it
- Zhenya (6/30) Jan 14 2013 I do not agree with you, static attribute is not a small detail.
Hi!
Is it all right with it:
struct Foo
{
struct Bar
{
void opCall()
{
writeln("non-static");
}
}
Bar bar;
static struct Anotherbar
{
static void bar()
{
writeln("static");
}
}
alias Anotherbar this;
}
void main()
{
Foo f;
f.bar();
Foo.bar();//fils with message:type Bar is not an expression
Foo.Bar b;
b();//this works however
}
?
Jan 13 2013
On Sunday, 13 January 2013 at 19:16:36 UTC, Zhenya wrote:
Hi!
Is it all right with it:
struct Foo
{
struct Bar
{
void opCall()
{
writeln("non-static");
}
}
Bar bar;
static struct Anotherbar
{
static void bar()
{
writeln("static");
}
}
alias Anotherbar this;
}
void main()
{
Foo f;
f.bar();
Foo.bar();//fils with message:type Bar is not an expression
Foo.Bar b;
b();//this works however
}
?
According to spec http://dlang.org/class.html#AliasThis undefined
lookups are forwarded to AliasThis member. But in your case Foo
struct has bar member, so no further resolution is performed.
Rename the member and the code compiles.
Note, this seems to come from neighbor thread
http://forum.dlang.org/thread/uelmpwwckcveimpbdtdo forum.dlang.org.
I think it is simpler to rename functions than create bunch of
structs just to be able to have eponymous non-static and static
functions.
Jan 13 2013
On Sunday, 13 January 2013 at 19:35:08 UTC, Maxim Fomin wrote:On Sunday, 13 January 2013 at 19:16:36 UTC, Zhenya wrote:I just want very much avoid renaming function,it's principle for me. So I would like to know is my sample right or no.Hi! Is it all right with it: struct Foo { struct Bar { void opCall() { writeln("non-static"); } } Bar bar; static struct Anotherbar { static void bar() { writeln("static"); } } alias Anotherbar this; } void main() { Foo f; f.bar(); Foo.bar();//fils with message:type Bar is not an expression Foo.Bar b; b();//this works however } ?According to spec http://dlang.org/class.html#AliasThis undefined lookups are forwarded to AliasThis member. But in your case Foo struct has bar member, so no further resolution is performed. Rename the member and the code compiles. Note, this seems to come from neighbor thread http://forum.dlang.org/thread/uelmpwwckcveimpbdtdo forum.dlang.org. I think it is simpler to rename functions than create bunch of structs just to be able to have eponymous non-static and static functions.
Jan 13 2013
On Sunday, January 13, 2013 20:41:48 Zhenya wrote:On Sunday, 13 January 2013 at 19:35:08 UTC, Maxim Fomin wrote:It functions exactly like it's supposed to. As Maxim said, undefined lookups go to the alias this member. If Foo already has a bar and you try and call it, it doesn't matter what Foo is aliased to, it's Foo's bar that's going to be used. - Jonathan M DavisAccording to spec http://dlang.org/class.html#AliasThis undefined lookups are forwarded to AliasThis member. But in your case Foo struct has bar member, so no further resolution is performed. Rename the member and the code compiles. Note, this seems to come from neighbor thread http://forum.dlang.org/thread/uelmpwwckcveimpbdtdo forum.dlang.org. I think it is simpler to rename functions than create bunch of structs just to be able to have eponymous non-static and static functions.I just want very much avoid renaming function,it's principle for me. So I would like to know is my sample right or no.
Jan 13 2013
"Zhenya" <zheny list.ru> On Sunday, 13 January 2013 at 22:36:03 UTC, Jonathan M Davis wrote:On Sunday, January 13, 2013 20:41:48 Zhenya wrote:Now it's clear for me,thank you.On Sunday, 13 January 2013 at 19:35:08 UTC, Maxim Fomin wrote:It functions exactly like it's supposed to. As Maxim said, undefined lookups go to the alias this member. If Foo already has a bar and you try and call it, it doesn't matter what Foo is aliased to, it's Foo's bar that's going to be used. - Jonathan M DavisAccording to spec http://dlang.org/class.html#AliasThis undefined lookups are forwarded to AliasThis member. But in your case Foo struct has bar member, so no further resolution is performed. Rename the member and the code compiles. Note, this seems to come from neighbor thread http://forum.dlang.org/thread/uelmpwwckcveimpbdtdo forum.dlang.org. I think it is simpler to rename functions than create bunch of structs just to be able to have eponymous non-static and static functions.I just want very much avoid renaming function,it's principle for me. So I would like to know is my sample right or no.
Jan 14 2013
On Sunday, 13 January 2013 at 22:36:03 UTC, Jonathan M Davis wrote:On Sunday, January 13, 2013 20:41:48 Zhenya wrote:import std.stdio; struct Bar { void opDispatch(string op)() if(op == "bar") { if(this !is m_init) writeln("non-static"); else writeln("maybe static"); } static property Bar m_init() { return Bar.init; } alias m_init this; } void main() { Bar b; Bar.bar(); readln; } If I understood you correctly, it must be compiled since there isn't some 'bar' that is going to be used, right? But it doesn't compile.On Sunday, 13 January 2013 at 19:35:08 UTC, Maxim Fomin wrote:It functions exactly like it's supposed to. As Maxim said, undefined lookups go to the alias this member. If Foo already has a bar and you try and call it, it doesn't matter what Foo is aliased to, it's Foo's bar that's going to be used. - Jonathan M DavisAccording to spec http://dlang.org/class.html#AliasThis undefined lookups are forwarded to AliasThis member. But in your case Foo struct has bar member, so no further resolution is performed. Rename the member and the code compiles. Note, this seems to come from neighbor thread http://forum.dlang.org/thread/uelmpwwckcveimpbdtdo forum.dlang.org. I think it is simpler to rename functions than create bunch of structs just to be able to have eponymous non-static and static functions.I just want very much avoid renaming function,it's principle for me. So I would like to know is my sample right or no.
Jan 14 2013
On Monday, January 14, 2013 17:57:03 Zhenya wrote:
import std.stdio;
struct Bar
{
void opDispatch(string op)()
if(op == "bar")
{
if(this !is m_init)
writeln("non-static");
else
writeln("maybe static");
}
static property Bar m_init()
{
return Bar.init;
}
alias m_init this;
}
void main()
{
Bar b;
Bar.bar();
readln;
}
If I understood you correctly, it must be compiled since there
isn't some 'bar' that is going to be used, right?
But it doesn't compile.
I honestly have no idea how opDispatch and alias this are supposed to
interact. They're both used as fallbacks when the type doesn't directly define
a function. That being said The reason that your code doesn't work here is the
fact that you'r ecalling bar is if it were a static function, but your
opDispatch isn't static. opDispatch would have to be static for it to be used
as a static function (it can't be both static and non-static), and in that
case, the if condition that you have in it wouldn't compile.
- Jonathan M Davis
Jan 14 2013
On Tuesday, 15 January 2013 at 00:04:15 UTC, Jonathan M Davis wrote:On Monday, January 14, 2013 17:57:03 Zhenya wrote::( If compiler tried alias this before opDispatch all would be OK. Maybe I'm going to give up. Thank you for comprehensive explanation.import std.stdio; struct Bar { void opDispatch(string op)() if(op == "bar") { if(this !is m_init) writeln("non-static"); else writeln("maybe static"); } static property Bar m_init() { return Bar.init; } alias m_init this; } void main() { Bar b; Bar.bar(); readln; } If I understood you correctly, it must be compiled since there isn't some 'bar' that is going to be used, right? But it doesn't compile.I honestly have no idea how opDispatch and alias this are supposed to interact. They're both used as fallbacks when the type doesn't directly define a function. That being said The reason that your code doesn't work here is the fact that you'r ecalling bar is if it were a static function, but your opDispatch isn't static. opDispatch would have to be static for it to be used as a static function (it can't be both static and non-static), and in that case, the if condition that you have in it wouldn't compile. - Jonathan M Davis
Jan 14 2013
I just want very much avoid renaming function,it's principle for me. So I would like to know is my sample right or no.I think that the main overall principle here is that is it impossible to have two functions which differ only by static attribute. I even do not imagine the use case of this. Well, here is the most natural way to achieve similar effect, I suppose: struct MyStruct { struct Static { static void myfun() { writeln("static myfun"); } } void myfun() { writeln("myfun"); } static Static opCall() { return Static(); } } MyStruct obj; obj.myfun(); //dynamic; MyStruct().myfun(); //static;
Jan 13 2013
On Sunday, 13 January 2013 at 23:21:20 UTC, Andrey wrote:I do not agree with you, static attribute is not a small detail. this reference is the same argument, like all the others. And despite the fact that function signatures are the same, the actual list of arguments are different.I just want very much avoid renaming function,it's principle for me. So I would like to know is my sample right or no.I think that the main overall principle here is that is it impossible to have two functions which differ only by static attribute. I even do not imagine the use case of this. Well, here is the most natural way to achieve similar effect, I suppose: struct MyStruct { struct Static { static void myfun() { writeln("static myfun"); } } void myfun() { writeln("myfun"); } static Static opCall() { return Static(); } } MyStruct obj; obj.myfun(); //dynamic; MyStruct().myfun(); //static;
Jan 14 2013