I want to express an equality like x=c as inequalities x -c <= 0 , x -c >= 0 . Having x = oo is a valid constraint, which is equiv to x -oo <= 0 and x =oo >= 0. Sure I can get rid of x -oo <= 0 but the whole point is that SAGE converts x-oo<=0 and x = oo >=0 to x - oo <= 0 and -Infinity >= 0. Which clearly kills the original semantics of (x -oo <= 0 and x =oo >= 0).
Also, why not have such a constraint ? it could mean I don't know the bound of x so I will totally over approximate it (to something that's always valid) On Tuesday, March 26, 2013 2:02:23 AM UTC-6, P Purkayastha wrote: > > On 03/26/2013 12:59 PM, tvn wrote: > > In my project I often have inequalities x <= c , x+y <= c, x -y <= c and > > to make things uniform, I move all the consts to the lhs, e.g. x <= c > > becomes x - c <= 0 . However this becomes problem when c is Infinity > > because Sage automatically converts x - oo <= 0 to -Infinity <= 0 and > > removes all variables in the original relation. Is there a way to get > > around this ? I thought about creating a new variable to represent oo > > but thought there could be easier way. > > > > In fact I am not so sure if such action is desirable, for example if I > > have x <= oo and x >= oo , this clearly implies x = oo . But treat > > these as -oo >= 0 and -oo <= 0 make no sense (-oo >= 0 is False). > > Sympy does not use this action and allows relations such as x - oo <= 0 > . > > Mathematically speaking, why would you want to have a constraint saying > x <= oo? This should behave the same as not having any constraint on x. > Perhaps I am not understanding what you want to constrain here. > > > > -- You received this message because you are subscribed to the Google Groups "sage-support" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/sage-support?hl=en. For more options, visit https://groups.google.com/groups/opt_out.
