Comment #23 on issue 1321 by asmeurer: trigonometric functions of
floating-point numbers should return floating-point numbers
http://code.google.com/p/sympy/issues/detail?id=1321
Well, we need to be consistent. A floating point number (Real) should
either absorb everything that can be evalf'd by default, or nothing. Right
now, we have:
In [45]: 3.5*pi
Out[45]: 3.5⋅π
In [46]: sqrt(3.5)
Out[46]: 1.87082869338697
In [47]: 3.5*sqrt(3)
Out[47]:
⎽⎽⎽
3.5⋅╲╱ 3
(obviously something like S(1.2)*S(3.4) should work no matter what).
I'm undecided on this. On the one hand, having a floating point number is
an explicit thing (as opposed to using exact numbers). On the other hand,
you know how I feel about automatic evaluation.
Also, it certainly seems like sin(0.5) should return a number. After all,
we try to make functions like sin return a number when given an exact
number where the value is known, like
In [48]: sin(pi/2)
Out[48]: 1
I think we should get ness's patch in (if it is ready to go), but
ultimately decide on how floating point numbers should work in SymPy.
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