Re: shifting bits

[Jim Rogers <jimmaureenrogers@worldnet.att.net>]

fmdf@tiscali.it (fabio de francesco) wrote in 
news:ba2f9c57.0408281738.61a48643@posting.google.com:

> Hello.
> 
> I had to pack/unpack some variables into/from one. In order to get the
> result I chose to shift the variables' bits using multiplications and
> divisions by powers of two.
> 
> 1) Does Ada have a built-in shift operand like C++ "<<" and ">>" ?

Ada provides similar bit shifting operations in the package Interfaces.
Those operations are defined for specific instances of modular types.

> 2) Can only variables of modular type be shifted ? If yes, why ?

Even in C and C++ bit shifting is only correct for unsigned types.
Think about what would happen if you shift a sign bit. The 
resulting values would be really nasty depending upon the state of
the sign bit.

Modular types are Ada's unsigned types.

Jim Rogers