

Am 21.12.2016 um 06:49 schrieb omniverse:
> Just looked at what clock says it is when trying equal frames.
>
> nan(ind)
>
> Not a number (with a dash, minus??), but I don't know what the ind means.
> Thought you probably would.
Yes: "Indeterminate". Meaning that the expression has no solution at all
(not even infinity), or that it has more than one solution (typically
infinitely many).
For example, the expression
a / b
is supposed to yield the number x that satisfies
x * b = a
so the expression
0 / 0
should yield the number x that satisfies
x * 0 = 0
which is true for all numbers, so the computer can't decide on any
particular one to give as a result.
At the other end of the spectrum, the expression
sqrt(1)
has no answer at all in the set of real numbers, so the computer is
again can't give you any meaningful result.
A slightly different case is the expression
1 / 0
for which some mathematical systems add two special values to the set of
real numbers, named "positive infinity" (defined as 1/0) and "negative
infinity" (defined as 1/0), so in this case the computer does have a
result to present  which is still "not a number" though, so it is
reported in a similar way:
nan(inf)
Not sure what that minus sign means. Might be just an intrinsic part of
the way "NotaNumber" values are reported, or might actually mean
_something_. Maybe the IEEE would know.
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