When I say that n is not predetermined, I mean that I want my script to work for any n. So before I define the polynomial ring, n is determined, but I want this to work for all n. So my question is how do I do the following.
n=6 R=PolynomialRing(QQ,n,'z') z=R.gens() g=sum(z[i] for i in range(n)) now how would I substitute into g the values z[i]=i? I want to keep n as a variable. On 7 June, 23:23, amps <[email protected]> wrote: > sorry, i meant > > g.subs({z[1]:value1...}) > > I am not sure why you call this intriguing syntax, but it is what > works. > > Example: > g=x+y > g.subs({x:2,y:4}) > 6 > > My problem is that I don't know how to do this if the number of > variables is not predetermined. > I tried to make a list with > a=list() > for i in range(n): > a.append(z[i]:value[i]) > but it does not like this kind of list (gives an error). > > you can think of it this way. Suppose n is not predetermined. > R=PolynomialRing(QQ,n,'z') > z=R.gens() > g=sum(z[i] for i in range(n)) > > now how would I substitute into g the values z[i]=i? > On 7 June, 21:48, "Justin C. Walker" <[email protected]> wrote: > > > On Jun 7, 2009, at 13:03 , amps wrote: > > > > I want to substitute n values into polynomial with n variables. > > > > I guess the syntax to do this is (if g is my polynomial with > > > indeterminates z[1], ..., z[n]). > > > > f.subs({z[1]:value1, z[2]:value2, ..., z[n]:valuen}) > > > > but how do I actually do this? n is not set, so I just can't type > > > this out. > > > That's intriguing syntax, but I don't think it will work. > > > Assuming that, at the call site, you know all your values, you can > > cobble up a tuple or list, something like the following: > > > L = [f(i+1) for i in range(n)] > > print g(L) > > > You can do this to determine 'n', assuming you don't know it at the > > call site: > > > n = len(g.variables()) > > > HTH > > > Justin > > > -- > > Justin C. Walker, Curmudgeon-At-Large > > Director > > Institute for the Enhancement of the Director's Income > > -------- > > "Weaseling out of things is what separates us from the animals. > > Well, except the weasel." > > - Homer J Simpson > > -------- --~--~---------~--~----~------------~-------~--~----~ To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/sage-support URLs: http://www.sagemath.org -~----------~----~----~----~------~----~------~--~---
