function sinc( x ) {
	if ( isnan( x ) ) {
		return NaN;
	}
	if ( isInfinite( x ) ) {
		return 0.0;
	}
	if ( x === 0.0 ) {
		return 1.0;
	}
	return sinpi( x ) / ( PI*x );
}
Computes the normalized cardinal sine of a number.

## Method

For \\( x \neq 0 \\), the normalized cardinal sine is calculated as

```tex
\operatorname{sinc}(x) = \frac{\operatorname{sin}(\pi x)}{\pi x}.
```

## Special Cases

```tex
\begin{align*}
\operatorname{sinc}(0) &= 1 & \\
\operatorname{sinc}(\infty) &= 0 & \\
\operatorname{sinc}(-\infty) &= 0 & \\
\operatorname{sinc}(\mathrm{NaN}) &= \mathrm{NaN}
\end{align*}
```

@param {number} x - input value
@returns {number} cardinal sine

@example
var v = sinc( 0.5 );
// returns ~0.637

@example
var v = sinc( -1.2 );
// returns ~-0.156

@example
var v = sinc( 0.0 );
// returns 1.0

@example
var v = sinc( NaN );
// returns NaN