NAN(P) POSIX Programmer's Manual NAN(P)
nan, nanf, nanl - return quiet NaN
double nan(const char *tagp);
float nanf(const char *tagp);
long double nanl(const char *tagp);
The function call nan("n-char-sequence") shall be equivalent to:
strtod("NAN(n-char-sequence)", (char **) NULL);
The function call nan("") shall be equivalent to:
strtod("NAN()", (char **) NULL)
If tagp does not point to an n- char sequence or an empty string, the function call shall
be equivalent to:
strtod("NAN", (char **) NULL)
Function calls to nanf() and nanl() are equivalent to the corresponding function calls to
strtof() and strtold().
These functions shall return a quiet NaN, if available, with content indicated through
If the implementation does not support quiet NaNs, these functions shall return zero.
No errors are defined.
The following sections are informative.
strtod() , strtold() , the Base Definitions volume of IEEE Std 1003.1-2001, <math.h>
Portions of this text are reprinted and reproduced in electronic form from IEEE Std
1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System
Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by
the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the
event of any discrepancy between this version and the original IEEE and The Open Group
Standard, the original IEEE and The Open Group Standard is the referee document. The orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 NAN(P)