function heavisidef( x, continuity ) {
	if ( isnanf( x ) ) {
		return NaN;
	}
	if ( x > 0.0 ) {
		return 1.0;
	}
	// Handle `+-0`...
	if ( x === 0.0 ) {
		if ( continuity === 'half-maximum' ) {
			return 0.5;
		}
		if ( continuity === 'left-continuous' ) {
			return 0.0;
		}
		if ( continuity === 'right-continuous' ) {
			return 1.0;
		}
		// Default behavior is discontinuity...
		return NaN;
	}
	return 0.0;
}
Evaluates the Heaviside function for a single-precision floating-point number.

@param {number} x - input value
@param {string} [continuity] - continuity option
@returns {number} function value

@example
var v = heavisidef( 3.14 );
// returns 1.0

@example
var v = heavisidef( -3.14 );
// returns 0.0

@example
var v = heavisidef( 0.0 );
// returns NaN

@example
var v = heavisidef( 0.0, 'half-maximum' );
// returns 0.5

@example
var v = heavisidef( 0.0, 'left-continuous' );
// returns 0.0

@example
var v = heavisidef( 0.0, 'right-continuous' );
// returns 1.0

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