Re: [Dev-C++] Character variables

[Ioannis V. <no...@ho...>]

-------Original Message-------=0D
 =0D
From: Per Westermark=0D
Date: =D4=E5=F4=DC=F1=F4=E7, 5 =CC=DC=F1=F4=E9=EF=F2 2003 2:04:36 =EC=EC=0D
To: Ioannis Vranos=0D
Cc: Dev-C++ Mailing List=0D
Subject: Re: [Dev-C++] Character variables=0D
 =0D
The shift operators are of course defiend for both signed and unsigned=0D
data types.=0D
=0D
It's just that for >> you may not assume if it will shift in a '0' or a=0D
'1' in the most significant bit fir signed integers, i.e.=0D
=0D
-3 (0xfffd) >> 1 =3D 32766 (0x7ffe)=0D
-3 (0xfffd) >> 1 =3D -2 (0xfffe)=0D
=0D
depending on implementation.=0D
=0D
However, when shifting in characters into a 32-bit integer, I don't have=0D
to care about this, since << always shifts in 0 in the least significant=0D
bit.=0D
=0D
=0D
=3D=3D> Yes bitwise operators can be applied to integral types signed and
unsigned however in signed types the behaviour is implementation
dependent/undefined. This is explicitly mentioned in the C99 standard:=0D
=0D
=3D=3D> "Some operators (the unary operator ~, and the binary operators <=
<, >>,
&, ^, and |,=0D
collectively described as bitwise operators) are required to have operand=
s
that have=0D
integer type. These operators return values that depend on the internal
representations of=0D
integers, and have implementation-defined and undefined aspects for signe=
d
types."=0D
=0D
=0D
=3D=3D> The above is not mentioned explicitly in the C++98 standard, but =
it is
common sense. That's why i spoke about bad magic. :)=0D
=0D
=0D
=0D
Ioannis Vranos=0D
=0D
* Programming pages: http://www.noicys.freeurl.com=0D
* Alternative URL: http://run.to/noicys=20