The function call nan("n-char-sequence") shall be equivalent
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
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 tagp.
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 original Standard can be obtained online at