Dear Vladimir, On Thu, 2006-03-09 at 16:31 +0000, Vladimir Kisil wrote:
"CD" == Chris Dams <Chris.Dams@mi.infn.it> writes: CD> ignored. Furthermore step(0)=1/2. This, however, should not be CD> taken too seriously as there is also the automatic evaluation CD> step(x)^2 -> step(x).
For a bigger consistency I would prefer to have either step(0)=0 or step(0)=1. Such a small features which is easy to overlook sometimes takes hours to realise.
Yes, that is a good point. I made step(0) equal to 1.
If three-values are really needed we may have another function sign(x)=1, x>0 sign(x)=0, x=0 sign(x)=-1, x<0
That function already more or less exists as csgn(x). The reason that it is useful to have both functions is that the combination (csgn(x)+1)/2 is kept together even when expanding and so on if one writes it as step(x). When looking at output it is more easy to see that step(P)*Q does not contribute if one knows that P happens to be negative then it is when it is to be canceled by another term equal to Q. Best wishes, Chris