Dear all,
I have been puzzled, and annoyed, by an unexpected side-effect. It
can be demonstrated in the notebook by the following example. It
models the speed as distance / time, then solve for the distance, then
evaluate the distance with different arguments:
var('v d t')
equation = v == d / t
solution = solve(equation, d, solution_dict = True)
d_ = solution[0][d]; print d_ #-> t*v
constants= {v: 2}
print d_(constants, t=3) #--> 6
# BEWARE: the previous call has the side effect that t=3 in later
evaluation !
print d_(constants) #--> 6 : the side-effect is apparent here !
print d_ #--> t*v
I would expect d_(constants) to result in t*2, but instead its using a
previous assignment of t to yield 6 !
I'm using Sage for an engineering pblm, and I find it useful to
separate constants from arguments. The side effect is thus annoying
to me: is there any other way to evaluate a function with constants
and arguments, without any side-effect with the arguments ? I'm new
to this forum, so not sure if it has been raised before. Sorry if
there is an easy answer.
Thanks in advance.
PC
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