Re: signatures

[Ehud Lamm <mslamm@mscc.huji.ac.il>]

On Thu, 29 Jul 1999, Brian Rogoff wrote:

|My preferred way would be
|
|generic 
|  type Item_Type is private;
|  type List_Type is array(Positive range <>) of Item_Type;
|with procedure Sort(S : in out List_Type) is <>;
|package Sort_Signature is end;
|
|then instantiate this with some types and a sort procedure. 

Yes, this seems like the natural way. But I don't like the idea of coding
a sort routine, which may not be conforming, and only thn using it to
instantiate a package, just to ensure the signature conformance. Am I
missing something/is theere an easier way?


|You can use
|this package as a package parameter to an implementation package like the 
|following.
|
|generic 
|  with My_Sort is new Sort_Signature(<>);
|package My_Package is 
|... etc
|
|A very nice addition to Ada over Ada-83, these package parameters and
|signature packages!
|

Indeed, and you can also code a package to be an instantiation! Like this
(from GNAT):

with Ada.Numerics.Long_Complex_Types
with Ada.Numerics.Generic_Complex_Elementary_Functions

package Ada.Numerics.Long_Complex_Elementary_Functions is
 new Ada.Numerics.Generic_Complex_Elementary_Functions
                (Ada.Numerics.Long_Complex_Types)


Ehud Lamm     mslamm@pluto.mscc.huji.ac.il
http://purl.oclc.org/NET/ehudlamm  <== My home on the web