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-- Copyright (C) 2002 Morgan Kaufmann Publishers, Inc
-- This file is part of VESTs (Vhdl tESTs).
-- VESTs is free software; you can redistribute it and/or modify it
-- under the terms of the GNU General Public License as published by the
-- Free Software Foundation; either version 2 of the License, or (at
-- your option) any later version.
-- VESTs is distributed in the hope that it will be useful, but WITHOUT
-- ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
-- FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
-- for more details.
-- You should have received a copy of the GNU General Public License
-- along with VESTs; if not, write to the Free Software Foundation,
-- Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
entity increment is
end entity increment;
architecture test of increment is
subtype word32 is bit_vector(31 downto 0);
-- code from book
procedure increment ( a : inout word32; by : in word32 := X"0000_0001" ) is
variable sum : word32;
variable carry : bit := '0';
begin
for index in a'reverse_range loop
sum(index) := a(index) xor by(index) xor carry;
carry := ( a(index) and by(index) ) or ( carry and ( a(index) xor by(index) ) );
end loop;
a := sum;
end procedure increment;
-- end code from book
begin
stimulus : process is
variable count : word32 := X"0001_1100";
begin
-- code from book (in text)
increment(count, X"0000_0004");
increment(count);
increment(count, by => open);
-- end code from book
wait;
end process stimulus;
end architecture test;
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