• Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> Jul 01 2012
• Nick Sabalausky <SeeWebsiteToContactMe semitwist.com> Jul 01 2012
• Walter Bright <newshound2 digitalmars.com> Jul 01 2012
• dennis luehring <dl.soluz gmx.net> Jul 01 2012
• dennis luehring <dl.soluz gmx.net> Jul 01 2012
• =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> Jul 02 2012
• Timon Gehr <timon.gehr gmx.ch> Jul 03 2012
• Jonathan M Davis <jmdavisProg gmx.com> Jul 01 2012
• "Kapps" <opantm2+spam gmail.com> Jul 01 2012
• Jonathan M Davis <jmdavisProg gmx.com> Jul 01 2012
• "xenon325" <1 mail.net> Jul 02 2012
• d coder <dlang.coder gmail.com> Jul 03 2012
• "bearophile" <bearophileHUGS lycos.com> Jul 03 2012
• Jonathan M Davis <jmdavisProg gmx.com> Jul 03 2012

Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> writes:

http://www.reddit.com/r/programming/comments/vvpfy/uniform_function_call_syntax_in_d_gamedevnet/

Andrei

Nick Sabalausky <SeeWebsiteToContactMe semitwist.com> writes:

On Sun, 01 Jul 2012 11:13:10 -0400
Andrei Alexandrescu <SeeWebsiteForEmail erdani.org> wrote:

 http://www.reddit.com/r/programming/comments/vvpfy/uniform_function_call_syntax_in_d_gamedevnet/
 
 Andrei


Good article.

One of the commenters brought up a point about confusion from possible
conflicts between UFCS funcs and member funcs. I was just about to
reply saying that's not an issue in D because it would be a conflict
error, but I did a little test first:

-----------------------
import std.stdio;

void bar(Foo f) {
    writeln("UFCS");
}

struct Foo {
    void bar() {
        writeln("Member");
    }
}

void main()
{
    Foo f;
    f.bar();
}
-----------------------

That successfully compiles and prints "Member". Same thing happens if
you move the UFCS func and Foo definition out into their own separate
modules. But I was expecting a conflict error at compile-time. Is this
a bug?

Walter Bright <newshound2 digitalmars.com> writes:

On 7/1/2012 11:53 AM, Nick Sabalausky wrote:
 That successfully compiles and prints "Member". Same thing happens if
 you move the UFCS func and Foo definition out into their own separate
 modules. But I was expecting a conflict error at compile-time. Is this
 a bug?



No, it's correct behavior. A real member overrides.

dennis luehring <dl.soluz gmx.net> writes:

Am 01.07.2012 23:02, schrieb Walter Bright:
 On 7/1/2012 11:53 AM, Nick Sabalausky wrote:
 That successfully compiles and prints "Member". Same thing happens if
 you move the UFCS func and Foo definition out into their own separate
 modules. But I was expecting a conflict error at compile-time. Is this
 a bug?



 No, it's correct behavior. A real member overrides.


isn't that some sort of highjacking then?

dennis luehring <dl.soluz gmx.net> writes:

Am 02.07.2012 07:13, schrieb Jonathan M Davis:
 On Monday, July 02, 2012 07:00:23 dennis luehring wrote:
 Am 01.07.2012 23:02, schrieb Walter Bright:
 On 7/1/2012 11:53 AM, Nick Sabalausky wrote:
 That successfully compiles and prints "Member". Same thing happens if
 you move the UFCS func and Foo definition out into their own separate
 modules. But I was expecting a conflict error at compile-time. Is this
 a bug?


 No, it's correct behavior. A real member overrides.


 isn't that some sort of highjacking then?


 More like it avoids hijacking. It stops you from creating a function which is
 used instead of the one which is on the class or struct.

 Granted, this does mean that you could be surprised about your external
 function not being called, and adding a new member function could cause your
 existing external function to no longer be called (which could be a problem),
 but realistically there's no other way to handle the situation. It's possible
 to explicitly give a path to the free function (e.g. path.to.function), but
 there's no way to do that for a member function, since there's only one way to
 call it. So, if you were forced to disambiguate, you could never indicate
 anything else other than the free function - not without introducing a new
 syntax to indicate the member function.

 - Jonathan M Davis


but the compiler selects the member-functions silently - thats odd, ok i 
will see it very fast - but then i need to change my code anyway - so 
whats the reason for the silent "overwrite"?

=?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:

On 07/01/2012 11:11 PM, Jonathan M Davis wrote:

 Yes, but as I said, if it _didn't_ select the member function when 


 conflict, it would be impossible to call the member function whenever 


 a conflict.


I wouldn't be a fan of it but I think it would still be possible:

class C
{
     void foo()
     {}
}

void main()
{
     auto c = new C();
     auto c_foo = &c.foo;
     c_foo();
}

Ali

Timon Gehr <timon.gehr gmx.ch> writes:

On 07/03/2012 09:55 PM, bearophile wrote:
 Jonathan M Davis:

 Yes, but as I said, if it _didn't_ select the member function when
 there was a
 conflict, it would be impossible to call the member function whenever
 there was
 a conflict. There is no way to indicate that you mean a member
 function rather
 than a free function. The normal way to do that is to use member
 function call
 syntax, and UFCS allows you to then use that for free functions. With
 conflicts
 between free functions, you can do path.to.func or other.place.func
 instead of
 just func, but with a member function, that's not possible. So,
 without adding
 new syntax to the language,


 I understand. This is Nick Sabalausky example:

 import std.stdio;

 void bar(Foo f) {
     writeln("UFCS");
 }

 struct Foo {
     void bar() {
         writeln("Member");
     }
 }

 void main()
 {
     Foo f;
     f.bar();
 }



 So let's assume the language gives an compile error here, because there
 is a conflict.


There is no conflict. The method takes precedence.

 If you want to call the free function you use bar(f). If
 you want to call the bar method of Foo, you can't, because it's
 ambiguous, and as you say there is no alternative (simple) syntax to
 specify you want the method of Foo.

 This is a limitation. But is this a problem?


Certainly.

 If you want to call Foo.bar
 then you don't import the free function bar in the current scope. How
 often do you want to keep both the free function and a method with the
 same name and you wan to call the method?


Every time you want the free function to be a generic implementation
that works for everything and the method to be a specialisation for the
respective type if present.

The question you should be asking is: "How often do you want to keep
both the function and a method with the same name and don't want to
call the method?" I cannot think of a single case.

 So maybe it's worth accepting this limitation, to reduce confusion for
 the people the read the code.


It does not do that.

It does not matter whether or not a function is a member function. Why
would it make any difference?

Jonathan M Davis <jmdavisProg gmx.com> writes:

On Monday, July 02, 2012 07:00:23 dennis luehring wrote:
 Am 01.07.2012 23:02, schrieb Walter Bright:
 On 7/1/2012 11:53 AM, Nick Sabalausky wrote:
 That successfully compiles and prints "Member". Same thing happens if
 you move the UFCS func and Foo definition out into their own separate
 modules. But I was expecting a conflict error at compile-time. Is this
 a bug?


 No, it's correct behavior. A real member overrides.


 isn't that some sort of highjacking then?


More like it avoids hijacking. It stops you from creating a function which is 
used instead of the one which is on the class or struct.

Granted, this does mean that you could be surprised about your external 
function not being called, and adding a new member function could cause your 
existing external function to no longer be called (which could be a problem), 
but realistically there's no other way to handle the situation. It's possible 
to explicitly give a path to the free function (e.g. path.to.function), but 
there's no way to do that for a member function, since there's only one way to 
call it. So, if you were forced to disambiguate, you could never indicate 
anything else other than the free function - not without introducing a new 
syntax to indicate the member function.

- Jonathan M Davis

"Kapps" <opantm2+spam gmail.com> writes:

On Monday, 2 July 2012 at 05:55:20 UTC, dennis luehring wrote:
 Am 02.07.2012 07:13, schrieb Jonathan M Davis:
 On Monday, July 02, 2012 07:00:23 dennis luehring wrote:
 Am 01.07.2012 23:02, schrieb Walter Bright:
 On 7/1/2012 11:53 AM, Nick Sabalausky wrote:
 That successfully compiles and prints "Member". Same thing 
 happens if
 you move the UFCS func and Foo definition out into their 
 own separate
 modules. But I was expecting a conflict error at 
 compile-time. Is this
 a bug?


 No, it's correct behavior. A real member overrides.


 isn't that some sort of highjacking then?


 More like it avoids hijacking. It stops you from creating a 
 function which is
 used instead of the one which is on the class or struct.

 Granted, this does mean that you could be surprised about your 
 external
 function not being called, and adding a new member function 
 could cause your
 existing external function to no longer be called (which could 
 be a problem),
 but realistically there's no other way to handle the 
 situation. It's possible
 to explicitly give a path to the free function (e.g. 
 path.to.function), but
 there's no way to do that for a member function, since there's 
 only one way to
 call it. So, if you were forced to disambiguate, you could 
 never indicate
 anything else other than the free function - not without 
 introducing a new
 syntax to indicate the member function.

 - Jonathan M Davis


 but the compiler selects the member-functions silently - thats 
 odd, ok i will see it very fast - but then i need to change my 
 code anyway - so whats the reason for the silent "overwrite"?


If it didn't overwrite silently, it would mean every single free 
function is now not a valid member function name. Better hope 
your users don't import a module that uses said free function.

In my opinion, the current way is the one that makes sense. And 
extension methods in C# do this as well.

Jonathan M Davis <jmdavisProg gmx.com> writes:

On Monday, July 02, 2012 07:54:56 dennis luehring wrote:
 Am 02.07.2012 07:13, schrieb Jonathan M Davis:
 On Monday, July 02, 2012 07:00:23 dennis luehring wrote:
 Am 01.07.2012 23:02, schrieb Walter Bright:
 On 7/1/2012 11:53 AM, Nick Sabalausky wrote:
 That successfully compiles and prints "Member". Same thing happens if
 you move the UFCS func and Foo definition out into their own separate
 modules. But I was expecting a conflict error at compile-time. Is this
 a bug?


 No, it's correct behavior. A real member overrides.


 isn't that some sort of highjacking then?


 More like it avoids hijacking. It stops you from creating a function which
 is used instead of the one which is on the class or struct.
 
 Granted, this does mean that you could be surprised about your external
 function not being called, and adding a new member function could cause
 your existing external function to no longer be called (which could be a
 problem), but realistically there's no other way to handle the situation.
 It's possible to explicitly give a path to the free function (e.g.
 path.to.function), but there's no way to do that for a member function,
 since there's only one way to call it. So, if you were forced to
 disambiguate, you could never indicate anything else other than the free
 function - not without introducing a new syntax to indicate the member
 function.
 
 - Jonathan M Davis


 but the compiler selects the member-functions silently - thats odd, ok i
 will see it very fast - but then i need to change my code anyway - so
 whats the reason for the silent "overwrite"?


Yes, but as I said, if it _didn't_ select the member function when there was a 
conflict, it would be impossible to call the member function whenever there was 
a conflict. There is no way to indicate that you mean a member function rather 
than a free function. The normal way to do that is to use member function call 
syntax, and UFCS allows you to then use that for free functions. With conflicts 
between free functions, you can do path.to.func or other.place.func instead of 
just func, but with a member function, that's not possible. So, without adding 
new syntax to the language, it was essentially impossible to do anything other 
than pick the member function whenever there's a conflict.

- Jonathan M Davis

"xenon325" <1 mail.net> writes:

On Monday, 2 July 2012 at 06:11:22 UTC, Jonathan M Davis wrote:
 So, without adding new syntax to the language, it was 
 essentially impossible to do anything other than pick the 
 member function whenever there's a conflict.


Thanks to C++ for inspiration, I even have proposal for such
syntax!

        obj.free myFunc( args )
        obj.member myFunc( args )

:D

d coder <dlang.coder gmail.com> writes:

--f46d04016c2935c63804c3ec0888
Content-Type: text/plain; charset=ISO-8859-1

 Thanks to C++ for inspiration, I even have proposal for such
 syntax!

        obj.free myFunc( args )
        obj.member myFunc( args )



obj.myFunc( args ); // calls member function, even if free function exists
myFunc( obj, args ); // calls free function, even if member function exists

That is the current behavior.  :-)

Regards
- Puneet

--f46d04016c2935c63804c3ec0888
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

<div class=3D"gmail_quote"><br><blockquote class=3D"gmail_quote" style=3D"m=
argin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div id=3D":5=
1q">Thanks to C++ for inspiration, I even have proposal for such<br>
syntax!<br>
<br>
=A0 =A0 =A0 =A0obj.free myFunc( args )<br>
=A0 =A0 =A0 =A0obj.member myFunc( args )<br><br></div></blockquote><div><br=
</div><div>How about:</div><div><br></div><div>obj.myFunc( args ); // call=


 ); // calls free function, even if member function exists</div>

<div><br></div><div>That is the current behavior. =A0:-)</div><div><br></di=
v><div>Regards</div><div>- Puneet</div><div><br></div></div>

--f46d04016c2935c63804c3ec0888--

"bearophile" <bearophileHUGS lycos.com> writes:

Jonathan M Davis:

 Yes, but as I said, if it _didn't_ select the member function 
 when there was a
 conflict, it would be impossible to call the member function 
 whenever there was
 a conflict. There is no way to indicate that you mean a member 
 function rather
 than a free function. The normal way to do that is to use 
 member function call
 syntax, and UFCS allows you to then use that for free 
 functions. With conflicts
 between free functions, you can do path.to.func or 
 other.place.func instead of
 just func, but with a member function, that's not possible. So, 
 without adding
 new syntax to the language,


I understand. This is Nick Sabalausky example:

 import std.stdio;

 void bar(Foo f) {
     writeln("UFCS");
 }

 struct Foo {
     void bar() {
         writeln("Member");
     }
 }

 void main()
 {
     Foo f;
     f.bar();
 }



So let's assume the language gives an compile error here, because 
there is a conflict. If you want to call the free function you 
use bar(f). If you want to call the bar method of Foo, you can't, 
because it's ambiguous, and as you say there is no alternative 
(simple) syntax to specify you want the method of Foo.

This is a limitation. But is this a problem? If you want to call 
Foo.bar then you don't import the free function bar in the 
current scope. How often do you want to keep both the free 
function and a method with the same name and you wan to call the 
method?

So maybe it's worth accepting this limitation, to reduce 
confusion for the people the read the code.

Bye,
bearophile

Jonathan M Davis <jmdavisProg gmx.com> writes:

On Tuesday, July 03, 2012 21:55:47 bearophile wrote:
 So maybe it's worth accepting this limitation, to reduce
 confusion for the people the read the code.


I would give a resounding no on that one. The confusion on how to actually 
manage to be able to use your member function would t hen be even greater, and 
if you need lots of other stuff from the module which provides the offending 
free function, then _not_ importing it becomes a royal pain. I think that the 
current approach works just fine.

- Jonathan M Davis