• bearophile <bearophileHUGS lycos.com> Dec 23 2010

bearophile <bearophileHUGS lycos.com> writes:

Simen kjaeraas:

 1:
 Tuple!(int, "a") a;
 Tuple!int b;
 b = a;
 
 IMO, this is good and correct. A tuple without field names is to me a
 mere black box with data inside, and throwing some other data in there
 is ok.


I agree.


 2:
 Tuple!( int, "a" ) a;
 Tuple!int b;
 a = b;
 
 This, I am not so sure about. A black box is turned into structured
 data. I guess it's ok.


I think it's OK. But the documentation needs to explain about this case.


 3:
 Tuple!( int, "a" ) a;
 Tuple!( int, "b" ) b;
 a = b;
 
 This I feel, is wrong. a is of a different type from b.


I think tuples are meant to be purely structural types, so even adding field
names they are compatibile. It's a design choice.

In Python they have recently added collections.namedtuple, they are tuples with
an optional name:
http://docs.python.org/dev/library/collections.html#collections.namedtuple

If Phobos tuple gain an optional name as I have once suggested, then two tuples
with different names are two different types (so we are back to nominative
typing).


 4:
 void foo( Tuple!int );
 Tuple!(int, "a") a;
 foo( a );
 
 This should work.


If the case 1) works, then this case too has to work.

Bye,
bearophile