March 15, 2006 NAN 3

### NAME

nan, nanf, nanl - return quiet NaN

### LIBRARY

Math Library (libm, -lm)

### SYNOPSIS

```double` nan(```const char *tagp`)
```float` nanf(```const char *tagp`)
```long` `double` nanl(```const char *tagp`)

### DESCRIPTION

The call nan(```"n-char-sequence"`) is equivalent to the call strod(```"NAN(n-char-sequence)"``, NULL`). The call nan(```""`) is equivalent to the call strod(```"NAN()"``, NULL`).

The nanf(``) and nanl(``) functions are equivalent to nan(``) but substituting strtof(``) and strtod(``), respectively.

### RETURN VALUES

#### IEEE 754

The nan(``), nanf(``), and nanl(``) functions return a quiet NaN as specified by ```tagp`.

#### VAX

The nan(``), nanf(``), and nanl(``) functions return zero.

### SEE ALSO

math(3), strod(3)

### STANDARDS

The nan(``), nanf(``), and nanl(``) functions conform to ISO/IEC 9899:1999 (``ISO C99'') .