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From: ma740988@gmail.com
Newsgroups: comp.lang.ada
Subject: if Restrict_Func /= null confusion
Date: Sun, 30 Mar 2008 13:58:02 -0700 (PDT)
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Date: 2008-03-30T13:58:02-07:00
List-Id: <comp.lang.ada>

Well folks its been at least 4 years since I've perused and/or written
Ada source.  That aside I'm perusing source code written in Ada.   So
consider:

-- used to restrict a variable within a range
-- for example: -PI to +PI
type Restrict_Function is access function (X: Real4) return Real4;

type Filt_Data is
  record
     Restrict_Func   : Restrict_Function ;

  end record ;


   --  within a procedure we have
  Fdata             : Filt_Data;
  Restrict_Func : Restrict_Function := FData.Restrict_Func ;

  if  Restrict_Func /= null then
   -- stuff
  endif

At issue:  I'm not following the conditional logic 'if (Restrict_Func /
= null)'.  Not understanding the impetus behind the check for null.