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From: hebisch@math.uni.wroc.pl (Waldek Hebisch)
Newsgroups: comp.lang.ada
Subject: Is this a gnat bug?
Date: 20 Sep 2003 22:50:11 GMT
Organization: Politechnika Wroclawska
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Date: 2003-09-20T22:50:11+00:00
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I am trying to convert a sequence of eight bytes to a fixed point
number. For testing I put bytes in an array. I first collect bytes
in a modular type and then assign the result to an integer (I have
eight bytes in big endian order, but the actual number should be
small). When number formed from 4 lower order bytes is out of
range I get CONSTRAINT_ERROR but if only higher order bytes are
non-zero I get just zero result. I would expect CONSTRAINT_ERROR 
always when any of higher order bytes is non-zero. With both 
gnat-3.14p and gnat from gcc-3.3 the program below prints huge
number for 'pp' and 0.0 for 'price'. 

with Ada.Text_IO;

procedure tstnum is 
type fx15_2 is delta 0.01 range -9999999999999.99 .. 9999999999999.99 ;
type price_type is delta 0.01 digits 6;

procedure getnum(num : out price_type) is 
  type ll is mod 2**64;
  type ip is range 0 .. 1000000 ;
  type byteind is range 0 .. 7;
  bytes : array (byteind) of integer range 0 .. 255 := (0..3 => 247 , 4..7=>0);
  pp : ll := 0 ;
  pp1 : ip;
begin
        for i in bytes'range loop
	        pp := pp * 256;
		pp := pp + ll(bytes(i));
	end loop;
	Ada.Text_IO.Put_Line("pp = " & ll'image(pp));
	pp1 := ip(pp); -- Should range check ??
	num := price_type(fx15_2(pp1)/100);
end;

price : price_type;

begin
	getnum(price);
	Ada.Text_IO.Put_Line("price = " & price_type'image(price));
end tstnum;


--
                              Waldek Hebisch
hebisch@math.uni.wroc.pl    or hebisch@hera.math.uni.wroc.pl