nan, nanf, nanl - return quiet NaN
double nan(const char *tagp);
float nanf(const char *tagp);
long double nanl(const char *tagp);
[CX] The functionality described on this reference page is aligned with the ISO C standard. Any conflict between the requirements described here and the ISO C standard is unintentional. This volume of IEEE Std 1003.1-2001 defers to the ISO C standard.
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 tagp.
If the implementation does not support quiet NaNs, these functions shall return zero.
No errors are defined.
strtod() , strtold() , the Base Definitions volume of IEEE Std 1003.1-2001, <math.h>
First released in Issue 6. Derived from the ISO/IEC 9899:1999 standard.