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digitalmars.D - And what will we do about package?

reply Don <nospam nospam.com> writes:
To quote bugzilla 143: 'package' does not work at all

But even if worked as advertised, it'd still be broken.

Although it's a really useful concept that works great in Java, the 
existing 'package' doesn't fit with D's directory-based module system.
As I see it, the problem is that, given:

module first.second.third.fourth;

which package is this module part of?
Is it 'third', 'second.third', or 'first.second.third'?

I think that _all_ of those can be reasonable project designs; but the 
compiler has no way of working out which is intended.
The behaviour currently described in the spec, that 'fourth' can use 
functions defined in 'first', is a particularly odd choice. If they were 
structs, the behaviour would be the exact opposite:

struct first {
    struct second {
       struct third {
            int fourth;
       }
    }
}
then first could access fourth, but fourth couldn't reach second. I 
think that's _generally_ the most sensible for modules, as well.

I think there are two possibilities:
(1) We work out some decent semantics for 'package'; OR
(2) We decide there isn't time, and defer it to D3.

Maybe the solution is a simple as adding a 'package' field to the module 
declaration. (eg,
module first.second.third.fourth package first.second;
)
But I fear that a major change to the module system might be required, 
which wouldn't be viable at this late stage.

Option (2) is possible because 'package' has never actually worked. It 
seems to be just a synonym for 'public' at present. Clearly, we can 
survive without it, no matter how desirable it is.
Nov 20 2009
next sibling parent "Denis Koroskin" <2korden gmail.com> writes:
On Fri, 20 Nov 2009 19:52:09 +0300, Don <nospam nospam.com> wrote:

 To quote bugzilla 143: 'package' does not work at all

 But even if worked as advertised, it'd still be broken.

 Although it's a really useful concept that works great in Java, the  
 existing 'package' doesn't fit with D's directory-based module system.
 As I see it, the problem is that, given:

 module first.second.third.fourth;

 which package is this module part of?
 Is it 'third', 'second.third', or 'first.second.third'?

 I think that _all_ of those can be reasonable project designs; but the  
 compiler has no way of working out which is intended.
 The behaviour currently described in the spec, that 'fourth' can use  
 functions defined in 'first', is a particularly odd choice. If they were  
 structs, the behaviour would be the exact opposite:

 struct first {
     struct second {
        struct third {
             int fourth;
        }
     }
 }
 then first could access fourth, but fourth couldn't reach second. I  
 think that's _generally_ the most sensible for modules, as well.

 I think there are two possibilities:
 (1) We work out some decent semantics for 'package'; OR
 (2) We decide there isn't time, and defer it to D3.

 Maybe the solution is a simple as adding a 'package' field to the module  
 declaration. (eg,
 module first.second.third.fourth package first.second;
 )
 But I fear that a major change to the module system might be required,  
 which wouldn't be viable at this late stage.

 Option (2) is possible because 'package' has never actually worked. It  
 seems to be just a synonym for 'public' at present. Clearly, we can  
 survive without it, no matter how desirable it is.

I never felt a need for "package" module attribute. But at class protection level, package implying final is ... ouch!
Nov 20 2009
prev sibling next sibling parent Yigal Chripun <yigal100 gmail.com> writes:
Don wrote:
 To quote bugzilla 143: 'package' does not work at all
 
 But even if worked as advertised, it'd still be broken.
 
 Although it's a really useful concept that works great in Java, the 
 existing 'package' doesn't fit with D's directory-based module system.
 As I see it, the problem is that, given:
 
 module first.second.third.fourth;
 
 which package is this module part of?
 Is it 'third', 'second.third', or 'first.second.third'?
 
 I think that _all_ of those can be reasonable project designs; but the 
 compiler has no way of working out which is intended.
 The behaviour currently described in the spec, that 'fourth' can use 
 functions defined in 'first', is a particularly odd choice. If they were 
 structs, the behaviour would be the exact opposite:
 
 struct first {
    struct second {
       struct third {
            int fourth;
       }
    }
 }
 then first could access fourth, but fourth couldn't reach second. I 
 think that's _generally_ the most sensible for modules, as well.
 
 I think there are two possibilities:
 (1) We work out some decent semantics for 'package'; OR
 (2) We decide there isn't time, and defer it to D3.
 
 Maybe the solution is a simple as adding a 'package' field to the module 
 declaration. (eg,
 module first.second.third.fourth package first.second;
 )
 But I fear that a major change to the module system might be required, 
 which wouldn't be viable at this late stage.
 
 Option (2) is possible because 'package' has never actually worked. It 
 seems to be just a synonym for 'public' at present. Clearly, we can 
 survive without it, no matter how desirable it is.

Well put. I think we can just drop "package" and adopt a similar model to that of Go with D modules. it looks simple and flexible. especially the ability to have a Go package span several files.
Nov 20 2009
prev sibling next sibling parent reply "Vladimir Panteleev" <thecybershadow gmail.com> writes:
On Fri, 20 Nov 2009 18:52:09 +0200, Don <nospam nospam.com> wrote:

 module first.second.third.fourth;
  which package is this module part of?
 Is it 'third', 'second.third', or 'first.second.third'?

Perhaps you meant: 'first', 'first.second', or 'first.second.third'? The case you mention presents an immediate ambiguity, but it is clarified by the module declaration or on the first import. If 'first.second.foo' imports 'first.second.third.bar' by 'import third.bar', and 'first.second.third.bar' has a module declaration or is imported from somewhere else using a different package "path", the compiler will generate an error ("Error: module X is in multiple packages Y") -- Best regards, Vladimir mailto:thecybershadow gmail.com
Nov 20 2009
parent reply Don <nospam nospam.com> writes:
Vladimir Panteleev wrote:
 On Fri, 20 Nov 2009 18:52:09 +0200, Don <nospam nospam.com> wrote:
 
 module first.second.third.fourth;
  which package is this module part of?
 Is it 'third', 'second.third', or 'first.second.third'?

Perhaps you meant: 'first', 'first.second', or 'first.second.third'?

 
 The case you mention presents an immediate ambiguity, but it is 
 clarified by the module declaration or on the first import. If 
 'first.second.foo' imports 'first.second.third.bar' by 'import 
 third.bar', and 'first.second.third.bar' has a module declaration or is 
 imported from somewhere else using a different package "path", the 
 compiler will generate an error ("Error: module X is in multiple 
 packages Y")

How do you define module fourth so that its 'package' functions are accesssable only to modules in first.second.* and not in first.* ?
Nov 20 2009
parent Mike Parker <aldacron gmail.com> writes:
Don wrote:
 Vladimir Panteleev wrote:
 On Fri, 20 Nov 2009 18:52:09 +0200, Don <nospam nospam.com> wrote:

 module first.second.third.fourth;
  which package is this module part of?
 Is it 'third', 'second.third', or 'first.second.third'?

Perhaps you meant: 'first', 'first.second', or 'first.second.third'?

 The case you mention presents an immediate ambiguity, but it is 
 clarified by the module declaration or on the first import. If 
 'first.second.foo' imports 'first.second.third.bar' by 'import 
 third.bar', and 'first.second.third.bar' has a module declaration or 
 is imported from somewhere else using a different package "path", the 
 compiler will generate an error ("Error: module X is in multiple 
 packages Y")

How do you define module fourth so that its 'package' functions are accesssable only to modules in first.second.* and not in first.* ?

You don't. The package in this case should be first.second.third and that's that. That's how it works in Java and is sometimes quite useful.
Nov 21 2009
prev sibling parent Lutger <lutger.blijdestijn gmail.com> writes:
Don wrote:

 To quote bugzilla 143: 'package' does not work at all
 
 But even if worked as advertised, it'd still be broken.
 
 Although it's a really useful concept that works great in Java, the
 existing 'package' doesn't fit with D's directory-based module system.
 As I see it, the problem is that, given:
 
 module first.second.third.fourth;
 
 which package is this module part of?
 Is it 'third', 'second.third', or 'first.second.third'?
 

Assuming you meant first, first.second and first.second.third, I'd say the most sensible choice is first.second.third (I actually assumed it works this way already). Why? Currently the most coarse level of granularity (excluding package) that has any meaning in D is the module level. If you want 'friend' access one step beyond that it only makes sense to choose the modules that map to the same directory. I'd like to think that is more than enough exposure for anyone. Anything beyond that seems way too promiscuous to me, like a poor substitute for C++'s friend.
Nov 21 2009