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From: addw@root44.UUCP
Newsgroups: net.lang.c
Subject: Re: Re: Problem in type conversion
Message-ID: <4232@root44.UUCP>
Date: Thu, 19-Jan-84 01:19:51 EST
Article-I.D.: root44.4232
Posted: Thu Jan 19 01:19:51 1984
Date-Received: Sat, 14-Jan-84 02:58:08 EST
Lines: 33

<<<<<To be eaten by mailers>>>>>
Roger L. Ferrel said:

>> What we see here with the:
>> 
>> 	inttype *= 0.5;
>> 		vs
>> 	inttype = inttype * 0.5;
>> 
>> is a weekness of most C compilers. It seems none of them handles float
>> operations very well when there are mixed types.  Of course the above is
>> a poor example since normally more efficent code would be generated by
>> using:
>> 
>> 	intype >>= 1;  /* how is this for getting off the subject? */

Unfortunately this is only guaranteed to work if:
1)	inttype is unsigned -plainly not the intention.
2)	inttype is positive, if inttype is negative it is undefined
what is put into the top bit; ie your negative number may become positive.
(A '1' will be inserted on a PDP11, but I assume that it is intended to write
portable programs. I don't know what other machines will do.)

There is little point in being efficient but wrong.
The only real alternative is:
	inttype /= 1;

	Alain Williams
	Root Computers Ltd, London.
	{ENGLAND}!ukc!root44!addw

PS, In England we spell the word that means 'lack of strength' as weakness,
& efficent as efficient.