• Jean-Louis Leroy (27/27) Jul 31 2018 How do I declare a variable that contains a pointer to a function
• Jean-Louis Leroy (3/30) Jul 31 2018 I know I could use `typeof(&bar) xpb = &bar;` but I wonder if
• John Colvin (10/37) Jul 31 2018 alias RefFuncT = ref int function(return ref int a);

Jean-Louis Leroy <jl leroy.nyc> writes:

How do I declare a variable that contains a pointer to a function 
returning a reference?

   import std.stdio;

   int foo(return ref int a)
   {
     a = 42;
     return a;
   }

   ref int bar(return ref int a)
   {
     a = 42;
     return a;
   }

   void main()
   {
     int x;
     auto apf = &foo;
     writeln(typeid(apf)); // int function(return ref int)*
     int function(return ref int) xpf = &foo;

     auto apb = &bar;
     writeln(typeid(apb)); // int function(return ref int) ref*

     // int function(return ref int) ref xpb = &bar; // Error: no 
identifier for declarator `int function(return ref int)`
     // ref int function(return ref int) xpb = &bar; // Error: 
variable `castfunc.main.xpb` only parameters or `foreach` 
declarations can be `ref`
   }

Jean-Louis Leroy <jl leroy.nyc> writes:

On Tuesday, 31 July 2018 at 21:29:26 UTC, Jean-Louis Leroy wrote:
 How do I declare a variable that contains a pointer to a 
 function returning a reference?

   import std.stdio;

   int foo(return ref int a)
   {
     a = 42;
     return a;
   }

   ref int bar(return ref int a)
   {
     a = 42;
     return a;
   }

   void main()
   {
     int x;
     auto apf = &foo;
     writeln(typeid(apf)); // int function(return ref int)*
     int function(return ref int) xpf = &foo;

     auto apb = &bar;
     writeln(typeid(apb)); // int function(return ref int) ref*

     // int function(return ref int) ref xpb = &bar; // Error: 
 no identifier for declarator `int function(return ref int)`
     // ref int function(return ref int) xpb = &bar; // Error: 
 variable `castfunc.main.xpb` only parameters or `foreach` 
 declarations can be `ref`
   }

I know I could use `typeof(&bar) xpb = &bar;` but I wonder if 
there is an explicit syntax.

John Colvin <john.loughran.colvin gmail.com> writes:

On Tuesday, 31 July 2018 at 21:29:26 UTC, Jean-Louis Leroy wrote:
 How do I declare a variable that contains a pointer to a 
 function returning a reference?

   import std.stdio;

   int foo(return ref int a)
   {
     a = 42;
     return a;
   }

   ref int bar(return ref int a)
   {
     a = 42;
     return a;
   }

   void main()
   {
     int x;
     auto apf = &foo;
     writeln(typeid(apf)); // int function(return ref int)*
     int function(return ref int) xpf = &foo;

     auto apb = &bar;
     writeln(typeid(apb)); // int function(return ref int) ref*

     // int function(return ref int) ref xpb = &bar; // Error: 
 no identifier for declarator `int function(return ref int)`
     // ref int function(return ref int) xpb = &bar; // Error: 
 variable `castfunc.main.xpb` only parameters or `foreach` 
 declarations can be `ref`
   }

alias RefFuncT = ref int function(return ref int a);

or

alias RefFuncT = typeof(&foo);

then

RefFuncT xpb = &bar;

or you can skip that and do

typeof(&bar) xpb = &bar;


P.S. next time this sort of question would be more appropriate in 
the the Learn forum