Am 05.06.2012 17:03, schrieb Brian Blais:
one small question: why did you change g=-9.8 to g=-Rational(98,10)?
does that make the analysis easier for sympy? is there some reason
to avoid floats?
Yes: 9.8 cannot be represented exactly in a machine float, it gets rounded.
In this case, this in itself isn't a problem, the round-off error is
orders of magnitudes smaller than the variance of g.
However, different machine architectures might implement the rounding
differently. There is a lot of nitty-gritty details about rounding, and
Python doesn't even attempt to control them. Which means that if you run
the program on a different machine, you may get different results. Which
is bad in a number of scenarios.
With Rational(98,10), this kind of thing doesn't happen because it's
using two integers and the division is never actually carried out.
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