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digitalmars.D - C#4 Covariance/Contravariance

reply bearophile <bearophileHUGS lycos.com> writes:
From the last C#:
http://codepad.org/kQgbwAqJ

Bye,
bearophile
Jun 07 2009
parent reply "Lionello Lunesu" <lionello lunesu.remove.com> writes:
"bearophile" <bearophileHUGS lycos.com> wrote in message 
news:h0ggl7$60f$1 digitalmars.com...

 From the last C#:
 http://codepad.org/kQgbwAqJ

 Bye,
 bearophile



Lionello likes this
Jun 09 2009
parent reply Robert Fraser <fraserofthenight gmail.com> writes:
Lionello Lunesu wrote:

 
 "bearophile" <bearophileHUGS lycos.com> wrote in message 
 news:h0ggl7$60f$1 digitalmars.com...

 From the last C#:
 http://codepad.org/kQgbwAqJ

 Bye,
 bearophile



 Lionello likes this



In D if you want to treat a Template!(SomeClass) as a Template!(Object), 
it's as easy as "cast(Template!(Object)) cast(void*) x"
Jun 09 2009
next sibling parent reply bearophile <bearophileHUGS lycos.com> writes:
Robert Fraser:

 In D if you want to treat a Template!(SomeClass) as a Template!(Object), 
 it's as easy as "cast(Template!(Object)) cast(void*) x"



How is this related to Covariance/Contravariance and in/out keywords, as shown
in C#4?

Bye,
bearophile
Jun 09 2009
parent reply Robert Fraser <fraserofthenight gmail.com> writes:
bearophile wrote:

 Robert Fraser:

 In D if you want to treat a Template!(SomeClass) as a Template!(Object), 
 it's as easy as "cast(Template!(Object)) cast(void*) x"



 How is this related to Covariance/Contravariance and in/out keywords, as shown
in C#4?
 
 Bye,
 bearophile



Errr... isn't that the point of covariance/contravariance?
Jun 09 2009
parent bearophile <bearophileHUGS lycos.com> writes:
Robert Fraser:

 Errr... isn't that the point of covariance/contravariance?



I don't know some of the things I post here. I just assume people here know
better than me.

Bye,
bearophile
Jun 10 2009
prev sibling parent reply "Lionello Lunesu" <lionello lunesu.remove.com> writes:
"Robert Fraser" <fraserofthenight gmail.com> wrote in message 
news:h0mui6$2rlh$1 digitalmars.com...

 Lionello Lunesu wrote:

 "bearophile" <bearophileHUGS lycos.com> wrote in message 
 news:h0ggl7$60f$1 digitalmars.com...

 From the last C#:
 http://codepad.org/kQgbwAqJ

 Bye,
 bearophile



 Lionello likes this



 In D if you want to treat a Template!(SomeClass) as a Template!(Object), 
 it's as easy as "cast(Template!(Object)) cast(void*) x"



Does not work for interfaces though.

L.
Jun 09 2009
parent Daniel Keep <daniel.keep.lists gmail.com> writes:
Lionello Lunesu wrote:

 
 "Robert Fraser" <fraserofthenight gmail.com> wrote in message
 news:h0mui6$2rlh$1 digitalmars.com...

 Lionello Lunesu wrote:

 "bearophile" <bearophileHUGS lycos.com> wrote in message
 news:h0ggl7$60f$1 digitalmars.com...

 From the last C#:
 http://codepad.org/kQgbwAqJ

 Bye,
 bearophile



 Lionello likes this



 In D if you want to treat a Template!(SomeClass) as a
 Template!(Object), it's as easy as "cast(Template!(Object))
 cast(void*) x"



 Does not work for interfaces though.
 
 L.



Hell, it's not even safe.

class Template(T)
{
    static T instance;
    final T getInstance() { return instance; }
}

Or

class Template(T)
{
    static if( is( T == SomeClass ) )
    {
        bool boom() { return true; }
    }
    void stuff();
}

(cast(Template!(Object)) cast(void*) new Template!(SomeClass)).stuff();
Jun 09 2009