Hi,
I have finally managed to try out Sage seriously after a long time
wanting to (and with intermediate-level Python experience). In general
it's really rather amazing, thanks to all involved!
I have come across what -- to me -- seems at least incongruous, when
substituting variables.
I am using 'Sage Version 4.4.4, Release Date: 2010-06-23', downloaded
a couple of days ago as the Ubuntu 10.04 binary package.
I want to have a variable called eps, but which appears as an epsilon
in the notebook interface, so I do
eps = var("epsilon")
Now suppose I have
a = 3 * eps
I now want to substitute eps=1, so I do
a.subs(eps = 1)
but the response is still 3*epsilon !
If I do
a.subs(epsilon = 1)
then I get 3.
But also, if I do
a.subs({eps:1})
with a dictionary instead, then I get what I expect, namely 3.
This seems to me strange, and possibly a bug, but maybe I'm just
misunderstanding.
Of course, I have found the solution -- just use a dictionary -- but I
would like to understand what's going on.
I see that the examples in the documentation seem always to use
variables defined simply as
var('x')
etc., whose names are equal to their representations, so this problem
seems not to arise.
Thanks and best wishes,
David.
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