A question relating to package interfaces.fortran

[Zheng Long Gen <zhenggen@public1.ptt.js.cn>]

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Hi, all,
    Forgive my ignorance, if this is a repeated post.
    In the following code, one tries to do math calculation on values of 
complex types defined in interfaces.fortran. 
-----------------------------------------------------------------------
with Interfaces.Fortran;
use Interfaces.Fortran;
with Ada.Numerics.Generic_Complex_Elementary_Functions;
procedure Complex_Type is
   package Complex_Elementary_Functions is 
      new Ada.Numerics.Generic_Complex_Elementary_Functions
     (Single_Precision_Complex_Types);
   use Complex_Elementary_Functions;
   C1,c2:Complex:=(0.5,0.0);
begin
   C2:=Sin(C1);
end;
------------------------------------------------------------------------
Compiling this piece of code(gnat 3.13p, Redhat 7.3.2)  will result in the 
following message:
gnatgcc -c -g -gnatq complex_type.adb
complex_type.adb:10:12: expected type 
"Ada.Numerics.Generic_Complex_Types.Complex" from instance at i-fortra.ads:37
complex_type.adb:10:12: found type "Interfaces.Fortran.Complex"

     package interfaces.fortran defines types to interface with fortran 
subprograms.  The complex  type is defined in the following way: (from RM 
B.5)
---------------------------------------------------------------------------
   package Single_Precision_Complex_Types is
      new Ada.Numerics.Generic_Complex_Types (Real);

   type Complex is new Single_Precision_Complex_Types.Complex;

   subtype Imaginary is Single_Precision_Complex_Types.Imaginary;
----------------------------------------------------------------------------
The problem is : 
    Type complex is a new type. It is different from its ancester defined in 
single_precision_complex_types. It should be a subtype of 
single_precision_complex_types.complex , just like the definition of "subtype 
Imaginary". Otherwise, it is totally useless. What do you think of it?

    Many thanks in advance.
    zhenggen
    20020301