How can I use the function in view of using segments?

[eluser]Unknown[/eluser]
code here
//------------
switch($this->uri->segment(2))
{
case 'login' : return login(); break;
case 'contact' : return contact(); break;
case 'products' : return products(); break;
case 'lang_change' : return lang_change(); break;
}
function login() {
echo "initializing login procedure";
}
function contact() {
echo "initializing cntact form";
}
.............