function ccis( z ) {
	var re;
	var im;
	var e;

	re = real( z );
	im = imag( z );

	sincos( re, WORKSPACE, 1, 0 );
	if ( im !== 0.0 ) {
		e = exp( -im );
		WORKSPACE[ 0 ] *= e;
		WORKSPACE[ 1 ] *= e;
	}
	return new Complex128( WORKSPACE[ 1 ], WORKSPACE[ 0 ] );
}
Evaluates the cis function for a double-precision complex floating-point number.

@param {Complex128} z - complex number
@returns {Complex128} result

@example
var Complex128 = require( '@stdlib/complex/float64/ctor' );
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );

var z = new Complex128( 0.0, 0.0 );
// returns <Complex128>

var out = ccis( z );
// returns <Complex128>

var re = real( out );
// returns 1.0

var im = imag( out );
// returns 0.0

@example
var Complex128 = require( '@stdlib/complex/float64/ctor' );
var real = require( '@stdlib/complex/float64/real' );
var imag = require( '@stdlib/complex/float64/imag' );

var z = new Complex128( 1.0, 0.0 );
// returns <Complex128>

var out = ccis( z );
// returns <Complex128>

var re = real( out );
// returns ~0.54

var im = imag( out );
// returns ~0.841