• Jonathan M Davis (11/11) Oct 07 2010 This has probably been brought up before, but given that the lack of def...
• Denis Koroskin (9/14) Oct 07 2010 Problem is that requirement is too restrictive. If ctor is pure, doesn't...
• Jonathan M Davis (5/21) Oct 07 2010 With the relaxed purity rules (which should be in the next release of dm...

Jonathan M Davis <jmdavisProg gmx.com> writes:

This has probably been brought up before, but given that the lack of default 
constructors for structs was a major problem for the QtD folks, I've been 
thinking about the problem again, and I was wondering whether it would work to 
have default constructors for structs as long as they were pure? Isn't the main 
problem with having default constructors for structs that the default 
constructor must result in the same value every time so that the compiler can 
set init appropriately? Or is there something else to it? It does seem to me 
that we should get default constructors for structs to work if we can. It's 
obviously been causing a problem in real code, including for major projects
like 
QtD.

- Jonathan M Davis

"Denis Koroskin" <2korden gmail.com> writes:

On Fri, 08 Oct 2010 03:31:54 +0400, Jonathan M Davis <jmdavisProg gmx.com>  
wrote:

 Isn't the main
 problem with having default constructors for structs that the default
 constructor must result in the same value every time so that the  
 compiler can
 set init appropriately?

Problem is that requirement is too restrictive. If ctor is pure, doesn't  
access globals and results in perfectly same objects, then why can't you  
do the initialization at compile-time? You usually can, that's not the  
issue.
The issue is that sometimes you need to call external functionals that are  
not pure in general (e.g. allocate some resources, initialize fields with  
unique values, register itself somewhere etc).

Jonathan M Davis <jmdavisProg gmx.com> writes:

On Thursday, October 07, 2010 16:42:47 Denis Koroskin wrote:
 On Fri, 08 Oct 2010 03:31:54 +0400, Jonathan M Davis <jmdavisProg gmx.com>
 
 wrote:
 Isn't the main
 problem with having default constructors for structs that the default
 constructor must result in the same value every time so that the
 compiler can
 set init appropriately?

 
 Problem is that requirement is too restrictive. If ctor is pure, doesn't
 access globals and results in perfectly same objects, then why can't you
 do the initialization at compile-time? You usually can, that's not the
 issue.
 The issue is that sometimes you need to call external functionals that are
 not pure in general (e.g. allocate some resources, initialize fields with
 unique values, register itself somewhere etc).

With the relaxed purity rules (which should be in the next release of dmd),
that 
problem should be somewhat mitigated. But you still won't be able to call 
globals.

- Jonathan M Davis