Negative of a scalar s ??

nikesh · March 19, 2013, 08:46

hii,
I have a small doubt I'd like to clarify. Hope somebody would help me out.
I understand that Positive of a scalar s is:

pos(s) = 1 if s>=0
= 0 if s<0

How can I express Negative of a scalar s?

neg(s) = ???

I'm assuming that this is possible BUT I find OpenFoam guide mentioning only about pos(s), but doesn't talk about neg(s). So just wanted to make sure.
I'm using OF version 1.7.1.

I'd appreciate any help.

Thanks in advance.
Nikesh.

mturcios777 · March 19, 2013, 11:11

I'm pretty sure there is a neg function, I did a quick search on the Doxygen docs and found several (in 2.2.x). You could also call pos(-s) and get near identical behaviour if your version of Foam doesn't have neg.

nikesh · March 19, 2013, 13:42

I tried using neg(s) in one of my codes and it does not seem to give me any error msg. But I'm still not sure what neg(s) would return.
neg(s) = ?

geth03 · May 25, 2020, 06:34

pos(s):
if s is positive or 0, then pos(s) = 1, else 0.

neg(s):
if s is negative, then neg(s) = 1, else 0.

March 19, 2013, 08:46	Negative of a scalar s ??	#1
nikesh Member Nikesh Bhattarai Join Date: Nov 2011 Location: Sacheon, South Korea Posts: 82 Rep Power: 13	hii, I have a small doubt I'd like to clarify. Hope somebody would help me out. I understand that Positive of a scalar s is: pos(s) = 1 if s>=0 = 0 if s<0 How can I express Negative of a scalar s? neg(s) = ??? I'm assuming that this is possible BUT I find OpenFoam guide mentioning only about pos(s), but doesn't talk about neg(s). So just wanted to make sure. I'm using OF version 1.7.1. I'd appreciate any help. Thanks in advance. Nikesh.

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March 19, 2013, 11:11		#2
mturcios777 Senior Member Marco A. Turcios Join Date: Mar 2009 Location: Vancouver, BC, Canada Posts: 740 Rep Power: 28	I'm pretty sure there is a neg function, I did a quick search on the Doxygen docs and found several (in 2.2.x). You could also call pos(-s) and get near identical behaviour if your version of Foam doesn't have neg.

March 19, 2013, 13:42		#3
nikesh Member Nikesh Bhattarai Join Date: Nov 2011 Location: Sacheon, South Korea Posts: 82 Rep Power: 13	I tried using neg(s) in one of my codes and it does not seem to give me any error msg. But I'm still not sure what neg(s) would return. neg(s) = ?

May 25, 2020, 06:34		#4
geth03 Senior Member Join Date: Dec 2019 Location: Cologne, Germany Posts: 355 Rep Power: 8	pos(s): if s is positive or 0, then pos(s) = 1, else 0. neg(s): if s is negative, then neg(s) = 1, else 0.