Updates:
Cc: Ronan.Lamy
Comment #25 on issue 1778 by smichr: Rational from string can be improved
http://code.google.com/p/sympy/issues/detail?id=1778
I suppose we could make Rational quite limited and strict, instantiating
from 1 or 2
integers/longs/Integers/Rationals: Rational(i, j=1) -> i/j. All the
manipulations of
strings and decision making about what is intended could be put in sympify
with, like
polys, a flag indicating how numbers should be handled, e.g.
S(expr, Q=True) -> expr with all numbers becoming instances of
Rational/Integer
S(expr, Z=True) -> expr with all numbers becoming instances of Real/Integer
Further, in the case of Q=True one should be able to signify whether the
numbers
should be converted approximately (e.g. as they would be represented by
str()) or
whether they should use full precision ('full' is the flag used by
nsimplify)
S(repr(.2), Q=True, full=True) -> 20000000000000001/100000000000000000
S(repr(.2), Q=True, full=False) -> 1/5
S('.23232323232323', Q=True, full=False) -> 23/99
I would vote for Q=True, full=False being the default so
S(1e2) -> 100 rather than 100.0 as it is now.
Any thoughts on this proposal?
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