var num = 0;
var img = new Array(images.length);

for(i = 0; i < images.length; i++)
{
     img[i] = new Image();
     img[i].src = images[i];
}

function diapo_suiv()
{
	num = (num + 1) % images.length;
	document.diaporama.src = img[num].src;
}

function diapo_prec()
{	
	if (num == 0)
		num = images.length - 1;
	else
		num--;
	document.diaporama.src = img[num].src;
}