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 GNU Scientific Library Reference Manual - Third Edition (v1.12) by M. Galassi, J. Davies, J. Theiler, B. Gough, G. Jungman, P. Alken, M. Booth, F. RossiPaperback (6"x9"), 592 pages, 60 figuresISBN 0954612078RRP £24.95 (\$39.95)

## 4.2 Infinities and Not-a-number

Macro: GSL_POSINF
This macro contains the IEEE representation of positive infinity, +\infty. It is computed from the expression +1.0/0.0.
Macro: GSL_NEGINF
This macro contains the IEEE representation of negative infinity, -\infty. It is computed from the expression -1.0/0.0.
Macro: GSL_NAN
This macro contains the IEEE representation of the Not-a-Number symbol, NaN. It is computed from the ratio 0.0/0.0.
Function: int gsl_isnan (const double x)
This function returns 1 if x is not-a-number.
Function: int gsl_isinf (const double x)
This function returns +1 if x is positive infinity, -1 if x is negative infinity and 0 otherwise.(4)
Function: int gsl_finite (const double x)
This function returns 1 if x is a real number, and 0 if it is infinite or not-a-number.
 ISBN 0954612078 GNU Scientific Library Reference Manual - Third Edition (v1.12) See the print edition