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From: tmoran@bix.com (Tom Moran)
Subject: Re: Ada.Streams examples
Date: 1999/03/17
Message-ID: <36f003ae.8532224@news.pacbell.net>#1/1
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Newsgroups: comp.lang.ada
Date: 1999-03-17T00:00:00+00:00
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>>   Someone could presumably do
>>      type GIFED_Bitmap is new BMP with null record;
>>      for GIFED_Bitmap'Write use  Convert_To_GIF_And_Write;
>> Then internally a GIFED_Bitmap is the same as my BMP, and my routines
>> all work on it, but when the user writes it he gets his
>> Convert_To_GIF_And_Write instead of my BMP'Write.

> I can think of several other objections, but they all really boil down to...YUK!
  He could certainly write his own Write_As_Gif(X : in BMP) and call
it directly.  Or I could make an abstract 'Write (or could I?) for BMP
and a higher level 
  type External_Form_Is_BMP is new BMP with null record;
with a 'Write that generates .bmp, and he could make instead
  type External_Form_Is_GIF is new BMP with null record;
etc.  
  I guess I don't react YUK.  A multiplatform GIF image seems to me
legitimately a higher abstraction level than a Windows DIBitmap/.bmp
file.