Nybble Help

Visitors can check out the Forum FAQ by clicking this link. You have to register before you can post: click the REGISTER link above to proceed. To start viewing messages, select the forum that you want to visit from the selection below. View our Forum Privacy Policy.
Want to receive the latest contracting news and advice straight to your inbox? Sign up to the ContractorUK newsletter here. Every sign up will also be entered into a draw to WIN £100 Amazon vouchers!

You are not logged in or you do not have permission to access this page. This could be due to one of several reasons:

You are not logged in. If you are already registered, fill in the form below to log in, or follow the "Sign Up" link to register a new account.
You may not have sufficient privileges to access this page. Are you trying to edit someone else's post, access administrative features or some other privileged system?
If you are trying to post, the administrator may have disabled your account, or it may be awaiting activation.

Churchill replied

12 July 2008, 07:45
Originally posted by NickFitz View Post

You can't - if the source, mask and destination are all the same location (i.e. the value at that location is XORed with itself and the result stored back into that location in one atomic operation), then the mask has become zero.

...and that wouldn't be very "sprite"ly from a software point of view, would it...?
Leave a comment:
NickFitz replied

12 July 2008, 02:22
Originally posted by DiscoStu View Post

I have absolutely no idea what any of you are talking about

That's why it's called an exclusive or
Leave a comment:
Diver replied

11 July 2008, 22:45
Originally posted by DiscoStu View Post

I have absolutely no idea what any of you are talking about

Never mind Junior

Before your time son
Leave a comment:
DiscoStu replied

11 July 2008, 22:18
I have absolutely no idea what any of you are talking about
Leave a comment:
lilelvis2000 replied

11 July 2008, 21:14
Nybble - that was a cool mag. dedicated to Apple II. i can remember entering hex code by hand from the pages. What was hilarious is watching terminator and seeing the code scroll by.
Leave a comment:
NickFitz replied

11 July 2008, 19:31
Originally posted by Churchill View Post

Take the 'mask' off.

You can't - if the source, mask and destination are all the same location (i.e. the value at that location is XORed with itself and the result stored back into that location in one atomic operation), then the mask has become zero.
Leave a comment:
Churchill replied

11 July 2008, 19:19
Originally posted by NickFitz View Post

Except in the case where you XOR it with itself... the first time will zero it, and the second will just leave it set to zero.

This is why the "swap two values without an intermediate location" trick only works if you can guarantee that the two locations holding the values are different.

Take the 'mask' off.
Leave a comment:
NickFitz replied

11 July 2008, 19:17
Originally posted by Churchill View Post

If you do it twice you'll be where you started.

See the (bit)pattern?

Except in the case where you XOR it with itself... the first time will zero it, and the second will just leave it set to zero.

This is why the "swap two values without an intermediate location" trick only works if you can guarantee that the two locations holding the values are different.
Leave a comment:
Churchill replied

11 July 2008, 18:50
If you do it twice you'll be where you started.

See the (bit)pattern?
Leave a comment:
Cliphead replied

11 July 2008, 18:29
Originally posted by DimPrawn View Post

If I XOR the upper Nybble of a tasty Byte, will I have more friends?

Only of a certain 'type'
Leave a comment:
DimPrawn started a topic Nybble Help

11 July 2008, 18:28
Nybble Help

If I XOR the upper Nybble of a tasty Byte, will I have more friends?
Tags: None