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NumberQ

FilledSmallSquare NumberQ[expr] gives True if expr is a number, and False otherwise.

FilledSmallSquare NumberQ[expr] returns False unless expr is manifestly a number (i.e., has head Complex, Integer, Rational or Real).

FilledSmallSquare NumberQ[Infinity] gives False.

FilledSmallSquare NumberQ[Overflow[ ]] and NumberQ[Underflow[ ]] give True.

FilledSmallSquare You can use NumberQ[x] ^= True to override the normal operation of NumberQ, and effectively define x to be a number.

FilledSmallSquare See Section 2.3.5 and Section 3.1.1.

FilledSmallSquare See also: NumericQ, IntegerQ, MachineNumberQ, TrueQ, Complexes.

FilledSmallSquare New in Version 1; modified in 3.

Further Examples