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From: henry@utzoo.UUCP (Henry Spencer)
Newsgroups: comp.lang.c,comp.misc
Subject: Re: 32bit = 16bit x 16bit (Really: Compiler deficiencies)
Message-ID: <8841@utzoo.UUCP>
Date: Wed, 28-Oct-87 12:46:43 EST
Article-I.D.: utzoo.8841
Posted: Wed Oct 28 12:46:43 1987
Date-Received: Wed, 28-Oct-87 12:46:43 EST
References: <141@kesmai.COM> 7349@alice.UUCP <146MAXHAM@RICE>, <593@l.cc.purdue.edu>
Organization: U of Toronto Zoology
Lines: 18

> ... I do not know of any language
> which has in its operation list an operation to multiply two 16 bit object
> and get a 32 bit object...

As has been said before, in C on a machine where shorts are 16 bits and longs
32, "(long)shortvar * (long)shortvar" does *exactly* this, assuming that the
compiler is smart enough to notice that it can do the casts as part of the
multiplication.  With the bonus that it works, although more slowly, even
if the compiler doesn't notice.

> ... How about the related problem of multiplying two 32 bit objects and
> getting a 64 bit object? ...

Given suitable data types (some 32-bit-machine C compilers have a "long long"
type for 64-bit integers), the same comment applies.
-- 
PS/2: Yesterday's hardware today.    |  Henry Spencer @ U of Toronto Zoology
OS/2: Yesterday's software tomorrow. | {allegra,ihnp4,decvax,utai}!utzoo!henry