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B.2 The Package Interfaces

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Package Interfaces is the parent of several library packages that declare types and other entities useful for interfacing to foreign languages. It also contains some implementation-defined types that are useful across more than one language (in particular for interfacing to assembly language). 

Static Semantics

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The library package Interfaces has the following skeletal declaration: 
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package Interfaces is
   pragma Pure(Interfaces);
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   type Integer_n is range -2**(n-1) .. 2**(n-1) - 1;  --2's complement
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   type Unsigned_n is mod 2**n;
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   function Shift_Left  (Value : Unsigned_n; Amount : Natural)
      return Unsigned_n;
   function Shift_Right (Value : Unsigned_n; Amount : Natural)
      return Unsigned_n;
   function Shift_Right_Arithmetic (Value : Unsigned_n; Amount : Natural)
      return Unsigned_n;
   function Rotate_Left  (Value : Unsigned_n; Amount : Natural)
      return Unsigned_n;
   function Rotate_Right (Value : Unsigned_n; Amount : Natural)
      return Unsigned_n;
   ...
end Interfaces;

Implementation Requirements

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An implementation shall provide the following declarations in the visible part of package Interfaces:
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10.1/2
   Support for interfacing to any foreign language is optional. However, an implementation shall not provide any attribute, library unit, or pragma having the same name as an attribute, library unit, or pragma (respectively) specified in the following clauses of this Annex unless the provided construct is either as specified in those clauses or is more limited in capability than that required by those clauses. A program that attempts to use an unsupported capability of this Annex shall either be identified by the implementation before run time or shall raise an exception at run time. 

Implementation Permissions

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An implementation may provide implementation-defined library units that are children of Interfaces, and may add declarations to the visible part of Interfaces in addition to the ones defined above.
11.1/2
   A child package of package Interfaces with the name of a convention may be provided independently of whether the convention is supported by the pragma Convention and vice versa. Such a child package should contain any declarations that would be useful for interfacing to the language (implementation) represented by the convention. Any declarations useful for interfacing to any language on the given hardware architecture should be provided directly in Interfaces.

Implementation Advice

12/2
 This paragraph was deleted.
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An implementation supporting an interface to C, COBOL, or Fortran should provide the corresponding package or packages described in the following clauses. 

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