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From: aschwarz@acm.org (skidmarks)
Newsgroups: comp.lang.ada
Subject: Re: Question about Ada.Unchecked_Conversion
Date: 30 Oct 2004 03:23:10 -0700
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Date: 2004-10-30T03:23:10-07:00
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I don't have the full picture of what you're trying to do so my answer
may be off the mark.

When I build a custom lexor I include a (usually) 256 cell array. The
cell is mapped one-to-one with (any) 256 representation of the
character set in use, and 256 has the property of guaranteeing nor
constraint errors. The contents of each cell is a enumeration
representing the purpose of the mapped character. My lexer is built
around this.

For example:

  type enum { ign, sep, op, sym, num, hex, ... );

  type enum_Map is array ( Integer range 1 .. 256 ) of enum;

  Map : constant enum_Map := ( ign, ... sep, ... );

begin -- 

   if ( enum_Map( Character'Pos(char) ) = <> ) then <> end if;


or

   case enum_Map( Character'Pos(char) ) is
   when ign => <>
   when sep => <>
   when op  => <>
   when sym => <>
   when num => <>
  
 and so on.

I use a Moore Machine for my finite state machine, the arcs
representing the transition states (ign, sep, ...) and actions
associated with taking the transition.

Hope this helps.

art