On 19/07/2018 12:18 AM, Charles Mills wrote:
I thought -16 was kind of cool. It took me a second, but in the future I would
"get" an & with -8 or -4 in a heartbeat.
It just looks wrong to me ;)
I don't know that ~15 or ~0xf is any clearer. ~ always worries me a little bit
for some reason.
Why does it worry you? To the majority of C programmers it's the natural
way of ANDing bits.
If you put your assembler programmers hat on
flag &= ~(BIT1)
isn't too dissimilar to
NI FLAG1,X'FF'-BIT1
I probably would have coded 0xfffffff0 but "counting nibbles" is error-prone
also.
Much better IMO!
Perhaps (-1) << 4 is arguably the most straightforward, but it's not obvious
either. Perhaps put into a macro?
Personally, I find that obscure.
Charles
-----Original Message-----
From: IBM Mainframe Discussion List [mailto:IBM-MAIN@LISTSERV.UA.EDU] On Behalf
Of David Crayford
Sent: Wednesday, July 18, 2018 5:45 AM
To: IBM-MAIN@LISTSERV.UA.EDU
Subject: Re: S0C6 in CSRC4RG1
On 18/07/2018 8:26 PM, Steve Smith wrote:
Nice...
So, you say 1s-complement is better than 2s-complement? Is ~15 clearer
than -16? ;-)
I say it's best to stick to the idioms of the language you're coding in :)
My "native" language is assembler, and it doesn't have an easy way to
specify the former.
Bit twiddling in C can be tricky and not as intuitive as assembler. But
it's trivial to write macros to make it easy.
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