ref: 469573c3fe8a09a2b5a1607188f4e52f6f8bee10
dir: /sys/man/2/nan/
.TH NAN 2 .SH NAME NaN, Inf, isNaN, isInf \- not-a-number and infinity functions .SH SYNOPSIS .B #include <u.h> .br .B #include <libc.h> .PP .ta \w'\fLdouble 'u .B double NaN(void) .PP .B double Inf(int) .PP .B int isNaN(double) .PP .B int isInf(double, int) .SH DESCRIPTION The IEEE floating point standard defines values called `not-a-number' and positive and negative `infinity'. These values can be produced by such things as overflow and division by zero. Also, the library functions sometimes return them when the arguments are not in the domain, or the result is out of range. By default, manipulating these values may cause a floating point exception on some processors but .I setfcr (see .IR getfcr (2)) can change that behavior. .PP .I NaN returns a double that is not-a-number. .I IsNaN returns true if its argument is not-a-number. .PP .IR Inf ( i ) returns positive infinity if .I i is greater than or equal to zero, else negative infinity. .I IsInf returns true if its first argument is infinity with a sign matching the second argument. A zero sign matches both negative and positive infinities. .SH SOURCE .B /sys/src/libc/port/nan.c .SH "SEE ALSO" .IR getfcr (2)