ixToString(m)
{
    var r = m.elements;
    var s = 
         '[ ' +toFixedWidth(r[0])+', '+toFixedWidth(r[4])+', '+toFixedWidth(r[8])+';\n'
        +'  ' +toFixedWidth(r[1])+', '+toFixedWidth(r[5])+', '+toFixedWidth(r[9])+';\n'
        +'  ' +toFixedWidth(r[2])+', '+toFixedWidth(r[6])+', '+toFixedWidth(r[10])+' ]';    
    return s;
}
function highlight(id)
{
    document.getElementById(highlightedId).classList.remove('phigh');
    highlightedId = id;
    document.getElementById(id).classList.add('phigh');