Presumable its because the RR nan doesn't correctly convert to the SR nan:
sage: NaN.is_zero()
False
sage: SR(RR('nan')).is_zero()
True
On Monday, April 25, 2016 at 7:40:39 PM UTC+2, William wrote:
>
> For a problem set I'm making today, I made up a random symbolic function,
> then evaluated it and got confusing/inconsistent behavior. See below:
>
> ~$ sage-develop
> ┌────────────────────────────────────────────────────────────────────┐
> │ SageMath version 7.2.beta5, Release Date: 2016-04-21 │
> │ Type "notebook()" for the browser-based notebook interface. │
> │ Type "help()" for help. │
> └────────────────────────────────────────────────────────────────────┘
> ┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
> ┃ Warning: this is a prerelease version, and it may be unstable. ┃
> ┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
> sage: f(x) = e^(pi*x) + asin(x) + 1/(x^2 - x- e)
> sage: f(1.1) # should this be NaN since asin(x) not defined? What is
> this output!? Print bug?
> 1/(-e + 0.110000000000000) + e^(1.10000000000000*pi)
> sage: N(f(1.1)) # yep
> NaN
> sage: N(1/(-e + 0.110000000000000) + e^(1.10000000000000*pi)) # What?
> 31.2987079491022
> sage: f(1.1).simplify() # The NaN at the beginning makes sense...
> NaN + 1/(-e + 0.1100000000000001) + e^(1.1*pi)
>
> I'm worried maybe there is a printing bug or something in f(1.1)...
>
> --
> William (http://wstein.org)
>
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