comp.lang.idl-pvwave archive: archive » Re: Need help identifying left most zero bit

Home » Public Forums » archive » Re: Need help identifying left most zero bit

Show: Today's Messages :: Show Polls :: Message Navigator
E-mail to friend

Re: Need help identifying left most zero bit [message #30152 is a reply to message #30131]

Fri, 05 April 2002 11:40

TFE
Messages: 11
Registered: November 2001

Junior Member

Phil,

think this is close-

x=-8
for i=0,15 do begin
y = UINT(ISHFT(-x-1,i)) ; 2's comp to swap bits, start left shift and check
leftmost bit
if ((y AND '8000'X) EQ '8000'X) then begin
print, 'position =', 16-i
i=15 ; exit loop
endif
endfor

"Phil" <plmcelwee@yahoo.com> wrote in message
news:a3589d11.0204051007.10df5da6@posting.google.com...
> I'm working with negative (two's complement) 16-bit numbers and could
> use some help. What I'd like to do is have a function that will tell
> me the location of the left-most zero bit for any given negative
> 16-bit number. Here are some examples to illustrate my goal.
>
> if x = -2, which is 1111 1111 1111 1110, then return 1
> if x = -5, which is 1111 1111 1111 1011, then return 3
> if x = -15, which is 1111 1111 1111 0111, then return 4
> if x = -8, which is 1111 1111 1111 1000, then return 3
>
> Is there something built-in to IDL that will accomplish this? Or does
> anyone have any other suggestions?

Report message to a moderator

[Message index]

		Re: Need help identifying left most zero bit By: David Fanning on Sat, 06 April 2002 22:01
		Re: Need help identifying left most zero bit By: Pavel Romashkin on Sat, 06 April 2002 20:39
		Re: Need help identifying left most zero bit By: David Fanning on Sat, 06 April 2002 15:02
		Re: Need help identifying left most zero bit By: Pavel Romashkin on Sat, 06 April 2002 12:43
		Re: Need help identifying left most zero bit By: TFE on Fri, 05 April 2002 11:40
		Re: Need help identifying left most zero bit By: plmcelwee on Tue, 09 April 2002 16:53

Previous Topic:	Re: Interfacing the functions
Next Topic:	Does IDL have a #include functionality

-=] Back to Top [=-

[ Syndicate this forum (XML) ] [

] [

]

Current Time: Fri Oct 10 23:45:41 PDT 2025

Total time taken to generate the page: 1.52131 seconds