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digitalmars.D - Re: inner member classes in final outer class

reply coxalan <coxalan web.de> writes:
Bruno Medeiros Wrote:


 I was thinking the following:
 
    class Outer {
    }
 
    class Inner(alias outer) {
      static assert(is(outer : Outer)); // Just a check
    }
 
    final Outer o1 = new Outer();
    final Outer o2 = new Outer();
 
    void main() {
        Inner i1 = new Inner!(o1);
        Inner i2 = new Inner!(o1);
 
        Inner i3 = new Inner!(o2);
        Inner i4 = new Inner!(o2);
    }



Thanks. That looks quite promising.

But it does not compile for me:
test.d(12): class test.Inner(alias outer) is used as a type
test.d(12): variable test.main.i1 voids have no value


 Having each Inner class parameterized with an alias, is like having a 
 compile-time constant member (the outer variable). This poses some 
 restrictions though: the outer classes variables cannot be declared 
 inside functions (because variables inside functions cannot be used as 
 alias parameters),



I'm do not exactly understand that. Where can I find documentation on that?


 and the Inner classes are no longer compatible 
 (covariant) with each other, although you can create a common Inner 
 superclass.



That's ok. I always had the perception that o1.Inner and o2.Inner are different
types.

coxalan
Sep 16 2007
next sibling parent reply Matti Niemenmaa <see_signature for.real.address> writes:
coxalan wrote:

 Bruno Medeiros Wrote:
 

 I was thinking the following:

    class Outer {
    }

    class Inner(alias outer) {
      static assert(is(outer : Outer)); // Just a check
    }

    final Outer o1 = new Outer();
    final Outer o2 = new Outer();

    void main() {
        Inner i1 = new Inner!(o1);
        Inner i2 = new Inner!(o1);

        Inner i3 = new Inner!(o2);
        Inner i4 = new Inner!(o2);
    }



 Thanks. That looks quite promising.
 
 But it does not compile for me:
 test.d(12): class test.Inner(alias outer) is used as a type
 test.d(12): variable test.main.i1 voids have no value



Probably because he uses "Inner i[1234]" where he should use "Inner!(o[1234])
i[1234]". The easiest solution is to use "auto" on the left-hand side of the
assignments.

-- 
E-mail address: matti.niemenmaa+news, domain is iki (DOT) fi
Sep 16 2007
parent reply coxalan <coxalan web.de> writes:
Matti Niemenmaa Wrote:


 coxalan wrote:

 Bruno Medeiros Wrote:
 

 I was thinking the following:

    class Outer {
    }

    class Inner(alias outer) {
      static assert(is(outer : Outer)); // Just a check
    }

    final Outer o1 = new Outer();
    final Outer o2 = new Outer();

    void main() {
        Inner i1 = new Inner!(o1);
        Inner i2 = new Inner!(o1);

        Inner i3 = new Inner!(o2);
        Inner i4 = new Inner!(o2);
    }



 Thanks. That looks quite promising.
 
 But it does not compile for me:
 test.d(12): class test.Inner(alias outer) is used as a type
 test.d(12): variable test.main.i1 voids have no value



 Probably because he uses "Inner i[1234]" where he should use "Inner!(o[1234])
 i[1234]". The easiest solution is to use "auto" on the left-hand side of the
 assignments.



Thanks. Now I get:
test.d(5): static assert  is false

Disclaimer: I'm quite new to D.

coxalan
Sep 16 2007
parent reply Matti Niemenmaa <see_signature for.real.address> writes:
coxalan wrote:

 Matti Niemenmaa Wrote:

 coxalan wrote:

 Bruno Medeiros Wrote:


 I was thinking the following:

    class Outer {
    }

    class Inner(alias outer) {
      static assert(is(outer : Outer)); // Just a check
    }

    final Outer o1 = new Outer();
    final Outer o2 = new Outer();

    void main() {
        Inner i1 = new Inner!(o1);
        Inner i2 = new Inner!(o1);

        Inner i3 = new Inner!(o2);
        Inner i4 = new Inner!(o2);
    }




 But it does not compile for me:
 test.d(12): class test.Inner(alias outer) is used as a type
 test.d(12): variable test.main.i1 voids have no value



 i[1234]". The easiest solution is to use "auto" on the left-hand side of the
 assignments.



 Thanks. Now I get:
 test.d(5): static assert  is false
 
 Disclaimer: I'm quite new to D.



Alright, I took a closer look and this compiles:

class Outer {
}

class Inner(alias outer) {
	static assert(is(typeof(outer) : Outer)); // Just a check
}

final Outer o1;
final Outer o2;

static this() {
	o1 = new Outer;
	o2 = new Outer;
}

void main() {

	auto i1 = new Inner!(o1);
	auto i2 = new Inner!(o1);

	auto i3 = new Inner!(o2);
	auto i4 = new Inner!(o2);
}

-- 
E-mail address: matti.niemenmaa+news, domain is iki (DOT) fi
Sep 16 2007
next sibling parent coxalan <coxalan web.de> writes:
Matti Niemenmaa Wrote:


 coxalan wrote:

 Matti Niemenmaa Wrote:

 coxalan wrote:

 Bruno Medeiros Wrote:


 I was thinking the following:

    class Outer {
    }

    class Inner(alias outer) {
      static assert(is(outer : Outer)); // Just a check
    }

    final Outer o1 = new Outer();
    final Outer o2 = new Outer();

    void main() {
        Inner i1 = new Inner!(o1);
        Inner i2 = new Inner!(o1);

        Inner i3 = new Inner!(o2);
        Inner i4 = new Inner!(o2);
    }




 But it does not compile for me:
 test.d(12): class test.Inner(alias outer) is used as a type
 test.d(12): variable test.main.i1 voids have no value



 i[1234]". The easiest solution is to use "auto" on the left-hand side of the
 assignments.



 Thanks. Now I get:
 test.d(5): static assert  is false
 
 Disclaimer: I'm quite new to D.



 Alright, I took a closer look and this compiles:
 
 class Outer {
 }
 
 class Inner(alias outer) {
 	static assert(is(typeof(outer) : Outer)); // Just a check
 }
 
 final Outer o1;
 final Outer o2;
 
 static this() {
 	o1 = new Outer;
 	o2 = new Outer;
 }
 
 void main() {
 
 	auto i1 = new Inner!(o1);
 	auto i2 = new Inner!(o1);
 
 	auto i3 = new Inner!(o2);
 	auto i4 = new Inner!(o2);
 }



Thanks!
Sep 16 2007
prev sibling parent reply coxalan <coxalan web.de> writes:
Matti Niemenmaa Wrote:


 Alright, I took a closer look and this compiles:
 
 class Outer {
 }
 
 class Inner(alias outer) {
 	static assert(is(typeof(outer) : Outer)); // Just a check
 }
 
 final Outer o1;
 final Outer o2;
 
 static this() {
 	o1 = new Outer;
 	o2 = new Outer;
 }
 
 void main() {
 
 	auto i1 = new Inner!(o1);
 	auto i2 = new Inner!(o1);
 
 	auto i3 = new Inner!(o2);
 	auto i4 = new Inner!(o2);
 }
 
 -- 
 E-mail address: matti.niemenmaa+news, domain is iki (DOT) fi



One last question on this:
Is it possible to do the same with D version 1?

The current code comples with DMD v2.004, but with DMD 1.020 I get:

forum.d(16): Error: cannot modify final variable 'o1'
forum.d(17): Error: cannot modify final variable 'o2'

coxalan
Sep 20 2007
parent reply Matti Niemenmaa <see_signature for.real.address> writes:
coxalan wrote:

 Matti Niemenmaa Wrote:

 class Outer {
 }

 class Inner(alias outer) {
 	static assert(is(typeof(outer) : Outer)); // Just a check
 }

 final Outer o1;
 final Outer o2;

 static this() {
 	o1 = new Outer;
 	o2 = new Outer;
 }

 void main() {

 	auto i1 = new Inner!(o1);
 	auto i2 = new Inner!(o1);

 	auto i3 = new Inner!(o2);
 	auto i4 = new Inner!(o2);
 }



 Is it possible to do the same with D version 1?
 
 The current code comples with DMD v2.004, but with DMD 1.020 I get:
 
 forum.d(16): Error: cannot modify final variable 'o1'
 forum.d(17): Error: cannot modify final variable 'o2'



Make o1 and o2 const instead of final.

-- 
E-mail address: matti.niemenmaa+news, domain is iki (DOT) fi
Sep 20 2007
parent coxalan <coxalan web.de> writes:
Matti Niemenmaa Wrote:


 coxalan wrote:

 Matti Niemenmaa Wrote:

 class Outer {
 }

 class Inner(alias outer) {
 	static assert(is(typeof(outer) : Outer)); // Just a check
 }

 final Outer o1;
 final Outer o2;

 static this() {
 	o1 = new Outer;
 	o2 = new Outer;
 }

 void main() {

 	auto i1 = new Inner!(o1);
 	auto i2 = new Inner!(o1);

 	auto i3 = new Inner!(o2);
 	auto i4 = new Inner!(o2);
 }



 Is it possible to do the same with D version 1?
 
 The current code comples with DMD v2.004, but with DMD 1.020 I get:
 
 forum.d(16): Error: cannot modify final variable 'o1'
 forum.d(17): Error: cannot modify final variable 'o2'



 Make o1 and o2 const instead of final.
 
 -- 
 E-mail address: matti.niemenmaa+news, domain is iki (DOT) fi



Thanks!

~coxalan
Sep 20 2007
prev sibling parent "Jarrett Billingsley" <kb3ctd2 yahoo.com> writes:
"coxalan" <coxalan web.de> wrote in message 
news:fcji0p$1tos$1 digitalmars.com...

 Bruno Medeiros Wrote:

        Inner i1 = new Inner!(o1);
        Inner i2 = new Inner!(o1);

        Inner i3 = new Inner!(o2);
        Inner i4 = new Inner!(o2);
    }







 But it does not compile for me:
 test.d(12): class test.Inner(alias outer) is used as a type
 test.d(12): variable test.main.i1 voids have no value



Change those declarations of i1, i2... to something like:

auto i1 = new Inner!(o1);
auto i2 = new Inner!(o2);
Sep 16 2007