How to translate >> to VB

I've seen a syntax line in C like

*crcres = *crcres >> 1

does someone know what this does and how to write it in VB

Advanced thanks

It does a binary right-shift by one bit.

As far as I know, VB can't do that...

It's similar to this:

crcres = crcres \ 2

..but I don't think that maps exactly to the function you specified

Lokks like you're doing CRC32 - attached is a VB version plus dll

Quote:

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Originally posted by swatty
*crcres = *crcres >> 1

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Shoulda been

Code:

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(*crcres) >>= 1;

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=).

Z.

Yeah - like strlen is really something like:

Code:

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for(buf=string, i=0;*buf;buf++) i++; return i;

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when it's not assembler.

Our core C code is: -abstracted, inlined, jammed, proffed, and reduced to the max. But, that doesn't mean a new guy should ever try it.

/me completely fails to grok that last sentence...

You know it jim, but regardless, it should be drilled into the brain of newcomers that using the <operator>= operators when appropriate is GOOD!

=).

Z.

Z.
uh huh... But most people who post here couldn't really read the stuff. I routinely 'tone down' everything I post. The idea is to communicate, not obfuscate. 90% of what I do is in ANSI C.

Parksie -
don't you try to inline, jam, etc, your core code? ie., optimize the living doo-doo out of your code? Especially the core code - primitives? We clock() on everything because the stuff gets called hundreds of millions of times a day. Literally. 5% gets you five minutes.

We have tables that have 100 million+ records. Full table scans net lots of traffic into the core modules. For example, Archive-purge runs over 10 hours. We want it to run in 5 or less.
It cleans out datasets.

100 million... my mind boggles at that number =).

I know what you mean. Things that seem really obvious to me now wont even occur to someone who has only been using c/c++ for a few months... and again, in a year or so, there will be things that are just natural where they wouldnt even have occured to me now.

Z.

If you have such heavily frequented code you might consider writing the tightest loops in assembler.

To translate bitshifts to VB you can use division/multiplication, it's just that it is much slower.

var <<= i;
=
var = var * 2^i

var >>= i;
=
var = var / 2^i

Use the integer divide, in this case, as it is faster:

Code:

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var  = var \ 2^i

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Z.

And prduces better results, as you don't want it to be converted to a floating point number (usually).

Yupper.

Z.

Quote:

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Originally posted by jim mcnamara
Parksie -
don't you try to inline, jam, etc, your core code? ie., optimize the living doo-doo out of your code? Especially the core code - primitives? We clock() on everything because the stuff gets called hundreds of millions of times a day. Literally. 5% gets you five minutes.

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Yeah, I do. We have to do about 100 calculations per finite element, of which some meshes have a few hundred thousand.

I did some *really* horrible-looking parser code a few days ago, but it sped it up from 6 hours to about 40 seconds.

There's nothing wrong with optimising. Just don't do it too early. Get it working first! :)