Re: How do you bitwise operations in Ada '83 and '95

[Simon Wright <simon@pushface.org>]

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:

> I can't tell for C. Does ANSI C standard require (x<<1) == (x*2)?

From the Committee Draft WG14/N1124 of May 6 2005, p83, with minimal
editing,

4 The result of E1 << E2 is E1 left-shifted E2 bit positions; vacated
bits are filled with zeros. If E1 has an unsigned type, the value of
the result is E1�2^E2, reduced modulo one more than the maximum value
representable in the result type. If E1 has a signed type and
nonnegative value, and E1�2^E2 is representable in the result type,
then that is the resulting value; otherwise, the behavior is
undefined.
 
5 The result of E1 >> E2 is E1 right-shifted E2 bit positions. If E1
has an unsigned type or if E1 has a signed type and a nonnegative
value, the value of the result is the integral part of the quotient of
E1 / 2^E2. If E1 has a signed type and a negative value, the resulting
value is implementation-defined.