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Function SIGNUM

Syntax

  • signum numbersigned-prototype

Arguments and Values

Description

signum determines a numerical value that indicates whether number is negative, zero, or positive.

For a rational, signum returns one of -1, 0, or 1 according to whether number is negative, zero, or positive. For a float, the result is a float of the same format whose value is minus one, zero, or one. For a complex number z, (signum z) is a complex number of the same phase but with unit magnitude, unless z is a complex zero, in which case the result is z.

For rational arguments, signum is a rational function, but it may be irrational for complex arguments.

If number is a float, the result is a float. If number is a rational, the result is a rational. If number is a complex float, the result is a complex float. If number is a complex rational, the result is a complex, but it is implementation-dependent whether that result is a complex rational or a complex float.

Examples

(signum 0)

0

(signum 99)

1

(signum 4/5)

1

(signum -99/100)

-1

(signum 0.0)

0.0

(signum #c(0 33))

#C(0.0 1.0)

(signum #c(7.5 10.0))

#C(0.6 0.8)

(signum #c(0.0 -14.7))

#C(0.0 -1.0)

(eql (signum -0.0) -0.0)

true

Side Effects

None.

Affected By

None.

Exceptional Situations

None.

See Also

  • {\secref\FloatSubstitutability}

Notes

(signum x) ≡ (if (zerop x) x (/ x (abs x)))