• Sean Eskapp (2/2) Jan 06 2011 Is there a way to create a function pointer which returns a reference? I...
• Steven Schveighoffer (25/28) Jan 07 2011 int x;
• Simen kjaeraas (7/34) Jan 07 2011 It's a known problem, not sure if it is in Bugzilla though.

Sean Eskapp <eatingstaples gmail.com> writes:

Is there a way to create a function pointer which returns a reference? In all
the ways I've tried it, my return value becomes "not an lvalue".

"Steven Schveighoffer" <schveiguy yahoo.com> writes:

On Thu, 06 Jan 2011 22:37:07 -0500, Sean Eskapp <eatingstaples gmail.com>  
wrote:

 Is there a way to create a function pointer which returns a reference?  
 In all
 the ways I've tried it, my return value becomes "not an lvalue".


int x;
ref int foo()
{
     return x;
}

void main()
{
     auto func = &foo;
     pragma(msg, typeof(func).stringof);
     func() = 5;
}

compiles and outputs during compilation:

int function() ref

However, doing this:

int function() ref func = &foo;

results in an error:

testreffuncptr.d(9): no identifier for declarator int function()
testreffuncptr.d(9): semicolon expected, not 'ref'
testreffuncptr.d(9): found 'ref' instead of statement

So, yes, you can make one.  No you can't specifically type it ;)  You must  
use auto.  I find the type string extremely strange too.

I think this is bugzilla-worthy.

-Steve

"Simen kjaeraas" <simen.kjaras gmail.com> writes:

Steven Schveighoffer <schveiguy yahoo.com> wrote:

 On Thu, 06 Jan 2011 22:37:07 -0500, Sean Eskapp  
 <eatingstaples gmail.com> wrote:

 Is there a way to create a function pointer which returns a reference?  
 In all
 the ways I've tried it, my return value becomes "not an lvalue".


 int x;
 ref int foo()
 {
      return x;
 }

 void main()
 {
      auto func = &foo;
      pragma(msg, typeof(func).stringof);
      func() = 5;
 }

 compiles and outputs during compilation:

 int function() ref

 However, doing this:

 int function() ref func = &foo;

 results in an error:

 testreffuncptr.d(9): no identifier for declarator int function()
 testreffuncptr.d(9): semicolon expected, not 'ref'
 testreffuncptr.d(9): found 'ref' instead of statement

 So, yes, you can make one.  No you can't specifically type it ;)  You  
 must use auto.  I find the type string extremely strange too.

 I think this is bugzilla-worthy.

It's a known problem, not sure if it is in Bugzilla though.
Workaround:

     alias ref int function() rifn;
     rifn fn = &foo;


-- 
Simen