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digitalmars.D.learn - define methods apart

reply spir <denis.spir gmail.com> writes:
Hello,


I cannot find a way to define methods (I mean "member functions) outside th=
e main type-definition body:

struct X {}
void X.say () {writeln("I say!");}
=3D=3D>
Element.d(85): semicolon expected, not '.'

Do I overlook anything, or is this simply impossible? In the latter case, w=
hat is the problem?
(In many languages, not only dynamic ones, method are or at least can be de=
fined apart.)


Denis
-- -- -- -- -- -- --
vit esse estrany =E2=98=A3

spir.wikidot.com
Dec 18 2010
next sibling parent bearophile <bearophileHUGS lycos.com> writes:
spir:

 Do I overlook anything, or is this simply impossible?

Even if you find some trick to do it, it's not the D way. A language syntax is defined by its conventions too. Bye, bearophile
Dec 18 2010
prev sibling next sibling parent reply Christopher Nicholson-Sauls <ibisbasenji gmail.com> writes:
On 12/18/10 07:19, spir wrote:
 Hello,
 
 
 I cannot find a way to define methods (I mean "member functions) outside the
main type-definition body:
 
 struct X {}
 void X.say () {writeln("I say!");}
 ==>
 Element.d(85): semicolon expected, not '.'
 
 Do I overlook anything, or is this simply impossible? In the latter case, what
is the problem?
 (In many languages, not only dynamic ones, method are or at least can be
defined apart.)
 
 
 Denis
 -- -- -- -- -- -- --
 vit esse estrany ☣
 
 spir.wikidot.com
 

As bearophile says, it just isn't the "D way" to do things. But, if you absolutely must (or just want to, for "playing" sakes) there are ways of faking it using opDispatch. Here's one I just tossed together and tested (DMD 2.050) right now. -------------------------------------------------- import std.stdio; class Foo { static addExternalMethod( void function( Foo ) fp, string id ) { _methodRegistry[ id ] = fp; } private static void function( Foo )[ string ] _methodRegistry; this ( string name ) { _name = name; } property const string name () { return _name; } private string _name; void opDispatch ( string Id ) () { if ( auto fp = Id in _methodRegistry ) { (*fp)( this ); } } } void _foo_sayHello (Foo self) { writefln( "Hello, I am %s.", self.name ); } static this () { Foo.addExternalMethod( &_foo_sayHello, "sayHello" ); } void main () { auto foo = new Foo( "Grant" ); foo.sayHello(); } -------------------------------------------------- Of course, there is the obvious issue of the 'method' signatures having to be the same, in this case. You'd have to find a better solution to the 'registry' issue, at the very least, in order to make it really usable. Generally speaking, though, I'm not sure what the real value would be in doing this in D. Did you have a particular use case in mind, or was it just idle exploration? -- Chris N-S
Dec 19 2010
parent Christopher Nicholson-Sauls <ibisbasenji gmail.com> writes:
On 12/19/10 06:52, spir wrote:
 On Sun, 19 Dec 2010 03:37:37 -0600
 Christopher Nicholson-Sauls <ibisbasenji gmail.com> wrote:
 
 On 12/18/10 07:19, spir wrote:
 Hello,


 I cannot find a way to define methods (I mean "member functions) outside the
main type-definition body:

 struct X {}
 void X.say () {writeln("I say!");}
 ==>
 Element.d(85): semicolon expected, not '.'

 Do I overlook anything, or is this simply impossible? In the latter case, what
is the problem?
 (In many languages, not only dynamic ones, method are or at least can be
defined apart.)


 Denis
 -- -- -- -- -- -- --
 vit esse estrany ☣

 spir.wikidot.com

As bearophile says, it just isn't the "D way" to do things. But, if you absolutely must (or just want to, for "playing" sakes) there are ways of faking it using opDispatch. Here's one I just tossed together and tested (DMD 2.050) right now. [code snipped] Generally speaking, though, I'm not sure what the real value would be in doing this in D. Did you have a particular use case in mind, or was it just idle exploration?

Thank you very for this example use of opdispatch :-) I'm still exploring the language (which I like very much, except for some given features *). Actually, I just wanted to know whether it's possible, because I'm used to this way and find it more practicle or readable in various cases. But it is not a problem. Denis (*) Some inherited from C/C++ (unhelpful syntax or semantics, mainly), some among the newest (too abstract or complicated, i'd say). -- -- -- -- -- -- -- vit esse estrany ☣ spir.wikidot.com

No problem. opDispatch has a number of possible uses. Another thing I've done with it before is to wrap the message passing system from std.concurrency, to ease defining message protocols. Basically I define a message as a struct, then define an opDispatch that looks for the pattern 'sendBLAH(...)' and forwards that to 'tid.send(BLAHMessage(...), thisTid())' auto-magically. To make it really magical I had to create some code-generation for the receiving end so it would provide an argument to receive/receiveTimeout for each handleBLAH method I define. It had a few little bugs/quirks though, which is why I haven't ever shared it. -- Chris N-S
Dec 20 2010
prev sibling parent spir <denis.spir gmail.com> writes:
On Sun, 19 Dec 2010 03:37:37 -0600
Christopher Nicholson-Sauls <ibisbasenji gmail.com> wrote:

 On 12/18/10 07:19, spir wrote:
 Hello,
=20
=20
 I cannot find a way to define methods (I mean "member functions) outsid=


=20
 struct X {}
 void X.say () {writeln("I say!");}
 =3D=3D>
 Element.d(85): semicolon expected, not '.'
=20
 Do I overlook anything, or is this simply impossible? In the latter cas=


 (In many languages, not only dynamic ones, method are or at least can b=


=20
=20
 Denis
 -- -- -- -- -- -- --
 vit esse estrany =E2=98=A3
=20
 spir.wikidot.com
=20

As bearophile says, it just isn't the "D way" to do things. =20 But, if you absolutely must (or just want to, for "playing" sakes) there are ways of faking it using opDispatch. Here's one I just tossed together and tested (DMD 2.050) right now. =20 [code snipped] Generally speaking, though, I'm not sure what the real value would be in doing this in D. Did you have a particular use case in mind, or was it just idle exploration?

Thank you very for this example use of opdispatch :-) I'm still exploring the language (which I like very much, except for some g= iven features *). Actually, I just wanted to know whether it's possible, be= cause I'm used to this way and find it more practicle or readable in variou= s cases. But it is not a problem. Denis (*) Some inherited from C/C++ (unhelpful syntax or semantics, mainly), some= among the newest (too abstract or complicated, i'd say). -- -- -- -- -- -- -- vit esse estrany =E2=98=A3 spir.wikidot.com
Dec 19 2010