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Newsgroups: comp.lang.ada
Date: Tue, 25 Aug 2015 08:26:24 -0700 (PDT)
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Subject: Re: Creating an empty file with Ada.Text_IO
From: Maciej Sobczak <see.my.homepage@gmail.com>
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Xref: news.eternal-september.org comp.lang.ada:27608
Date: 2015-08-25T08:26:24-07:00
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>    procedure Write_String_To_File (File_Name : in String; S : in String) is
>       A : Ada.Streams.Stream_Element_Array (1 .. S'Length);
>       F : Ada.Streams.Stream_IO.File_Type;
>    begin
>       -- convert S to stream elements
>       for I in S'Range loop
>          A (Ada.Streams.Stream_Element_Offset (I)) :=
>             Ada.Streams.Stream_Element (Character'Pos (S (I)));
>       end loop;

Before anybody uses it in a rocket - there is no provision above that S'First will be 1 and the indices might not be compatible in the above assignment.

Correct version is:

      for I in S'Range loop
         A (Ada.Streams.Stream_Element_Offset (I - S'First + 1)) :=
            Ada.Streams.Stream_Element (Character'Pos (S (I)));
      end loop;

And there are actually several ways to write it.
Now this procedure can write String slices that do not begin at index 1.

(Frankly, this part of Ada is inherently error-prone. I stumble on it repeatedly.)

-- 
Maciej Sobczak * http://www.inspirel.com