isANumber -- whether a number is not not-a-number

Synopsis

• Usage:

  isANumber x

• Inputs:
  • x, a number
• Outputs:
  • a Boolean value, whether x is not not a number.

Description

For a discussion of the notion of not-a-number in floating point arithmetic, see http://en.wikipedia.org/wiki/NaN.

i1 : isANumber 3.

o1 = true

i2 : inf = 1/0.

o2 = infinity

o2 : RR (of precision 53)

i3 : isANumber inf

o3 = true

i4 : nan = inf - inf

o4 = NotANumber

o4 : RR (of precision 53)

i5 : isANumber nan

o5 = false

See also

• isFinite -- whether a number is finite
• isInfinite -- whether a number is infinite