www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - interface final members

reply Joshua Reusch <yoschi arkandos.de> writes:
interface I {
	final int foo(I other, int a, int b) {
		return other.foo(a,b) + a*b;
	}
	int foo(int a, int b);
}

class A : I {
	int foo(int a, int b) {
		return a*b;
	}
}

void main() {
	A a = new A;

	a.foo(5,5);
	a.I.foo(a, 5,5);
	a.foo(a, 5,5); //line 22
}
---------
$ rdmd interface_final_test
interface_final_test.d(22): Error: function interface_final_test.A.foo 
(int a, int b) is not callable using argument types (A,int,int)
interface_final_test.d(22): Error: expected 2 arguments, not 3 for 
non-variadic function type int(int a, int b)
---------


Why do I need to write a.I.foo instead of a.foo to call the final method 
of the interface ?

Thank you, Joshua
Feb 21 2012
next sibling parent reply Mantis <mail.mantis.88 gmail.com> writes:
21.02.2012 14:46, Joshua Reusch пишет:

 interface I {
 final int foo(I other, int a, int b) {
 return other.foo(a,b) + a*b;
 }
 int foo(int a, int b);
 }

 class A : I {
 int foo(int a, int b) {
 return a*b;
 }
 }

 void main() {
 A a = new A;

 a.foo(5,5);
 a.I.foo(a, 5,5);
 a.foo(a, 5,5); //line 22
 }
 ---------
 $ rdmd interface_final_test
 interface_final_test.d(22): Error: function interface_final_test.A.foo 
 (int a, int b) is not callable using argument types (A,int,int)
 interface_final_test.d(22): Error: expected 2 arguments, not 3 for 
 non-variadic function type int(int a, int b)
 ---------


 Why do I need to write a.I.foo instead of a.foo to call the final 
 method of the interface ?

 Thank you, Joshua


I can't comment on the behaviour, but you may find this workaround useful:

class A : I {
alias I.foo foo;
int foo(int a, int b) {
return a*b;
}
}
Feb 21 2012
parent Jacob Carlborg <doob me.com> writes:
On 2012-02-21 14:15, Mantis wrote:

 21.02.2012 14:46, Joshua Reusch пишет:

 interface I {
 final int foo(I other, int a, int b) {
 return other.foo(a,b) + a*b;
 }
 int foo(int a, int b);
 }

 class A : I {
 int foo(int a, int b) {
 return a*b;
 }
 }

 void main() {
 A a = new A;

 a.foo(5,5);
 a.I.foo(a, 5,5);
 a.foo(a, 5,5); //line 22
 }
 ---------
 $ rdmd interface_final_test
 interface_final_test.d(22): Error: function interface_final_test.A.foo
 (int a, int b) is not callable using argument types (A,int,int)
 interface_final_test.d(22): Error: expected 2 arguments, not 3 for
 non-variadic function type int(int a, int b)
 ---------


 Why do I need to write a.I.foo instead of a.foo to call the final
 method of the interface ?

 Thank you, Joshua


 I can't comment on the behaviour, but you may find this workaround useful:

 class A : I {
 alias I.foo foo;
 int foo(int a, int b) {
 return a*b;
 }
 }


It's because the base class and the subclass use different overload 
sets, or something like that.

-- 
/Jacob Carlborg
Feb 21 2012
prev sibling parent reply =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 02/21/2012 04:46 AM, Joshua Reusch wrote:

 interface I {
 final int foo(I other, int a, int b) {
 return other.foo(a,b) + a*b;
 }
 int foo(int a, int b);
 }

 class A : I {
 int foo(int a, int b) {
 return a*b;
 }
 }

 void main() {
 A a = new A;

 a.foo(5,5);
 a.I.foo(a, 5,5);
 a.foo(a, 5,5); //line 22
 }
 ---------
 $ rdmd interface_final_test
 interface_final_test.d(22): Error: function interface_final_test.A.foo
 (int a, int b) is not callable using argument types (A,int,int)
 interface_final_test.d(22): Error: expected 2 arguments, not 3 for
 non-variadic function type int(int a, int b)
 ---------


 Why do I need to write a.I.foo instead of a.foo to call the final method
 of the interface ?

 Thank you, Joshua


Are you using 2.058? If so, this may be a bad interaction with the 
newly-added UFCS feature, which I haven't seen working yet. :)

The reason that I think so is that when the 'I other' is moved to a 
parameter location other than the first one, it works:

interface I {
     final int foo(int a, I other, int b) {// <- second parameter
         return other.foo(a,b) + a*b;
     }
     int foo(int a, int b);
}

class A : I {
     int foo(int a, int b) {
         return a*b;
     }
}

void main() {
     A a = new A;

     a.foo(5,5);
     a.I.foo(5, a, 5);
     a.foo(5,5); //line 22
}

I would say this warrants a bug report. The original code should have 
worked too.

Ali
Feb 21 2012
parent =?UTF-8?B?QWxpIMOHZWhyZWxp?= <acehreli yahoo.com> writes:
On 02/21/2012 09:58 AM, Ali Çehreli wrote:


 The reason that I think so is that when the 'I other' is moved to a
 parameter location other than the first one, it works:


No, it doesn't work. Sorry for the noise.

Ali
Feb 21 2012