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Date: Tue, 27 Sep 2005 16:08:36 +0200
From: Georg Bauhaus <bauhaus@futureapps.de>
Organization: future apps GmbH
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Newsgroups: comp.lang.ada
Subject: Re: String filtering
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Date: 2005-09-27T16:08:29+02:00
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David Trudgett wrote:

> Yes, well, functions work that way in Ada (fortunately, or
> unfortunately, I don't know). I could have made it a procedure with an
> "in out" parameter, but I like functional programming better.
> Unfortunately, I haven't been able to do proper functional style
> programming in Ada so far, having been thwarted by strong typing and
> lack of "out" parameters in functions.


Here's a filter then.

with Ada.Containers.Vectors;

package Character_Vectors is
   new Ada.Containers.Vectors(Element_Type => Character,
                              Index_Type => Positive);

with Character_Vectors;
with Ada.Strings.Maps.Constants;

procedure filter is

   use Character_Vectors;

   input: Vector;
   output: Vector;


   procedure save_good_ones(c: Cursor) is
      use Ada.Strings.Maps;

      Alpha_Num_Space_Set : constant Character_Set
        := Constants.Alphanumeric_Set or To_Set(' ');
   begin
      if Is_In(Element(c), Alpha_Num_Space_Set) then
         append(output, Element(c));
      end if;
   end save_good_ones;

begin
   Iterate(input, save_good_ones'access);
end filter;