Re: local variables

[dewar@merv.cs.nyu.edu (Robert Dewar)]

Tucker said

<<  package body Abstraction is
    procedure Op1(...) is
    begin
      -- do something interesting
    end Op1;

    Counter : Integer := 0;  -- "static" variable used by Bump_Counter
    procedure Bump_Counter(Next : out Integer) is
    begin
      Counter := Counter + 1;
      Next := Counter;
    end Bump_Counter;
  end Abstraction;
>>

You really don't need the relaxed rules of Ada 95 here, and indeed they
are not really sufficient in this case (what if there were another
routine after Bump_Counter, it would be able to see Counter, which is
wrong).

Instead you can just introduce a nested package:

  package body Abstraction is
    procedure Op1(...) is
    begin
      -- do something interesting
    end Op1;

    package body Encapsulate is

      Counter : Integer := 0;  -- "static" variable used by Bump_Counter
      procedure Bump_Counter(Next : out Integer) is
      begin
        Counter := Counter + 1;
        Next := Counter;
      end Bump_Counter;
    end Encapsulate;
  end Abstraction;


The corresponding package spec might have

  package Abstraction is
    procedure Op1(...);

    package Encapsulate is
      procedure Bump_Counter (Next : out Integer);
    end Encapsulate;

    procedure Bump_Counter (Next : out Integer)
      renames Encapsulate.Bump_Counter;

  end Abstraction;

and this can of course be done in Ada 83, so the reference to this as a
crippling problem seems overblown!