function AddParametro (Parametros, Parametro, Valor)
{
	if (Parametro != '')
	{	if (Parametros == '') return ('?' + Parametro + '=' + Valor);
		else return (Parametros + '&' + Parametro + '=' + Valor);
	} else return (Parametros);
}


function CadenaVacia (Cadena)
{
	return (Trim (Cadena) == '');
}


function CuentaSubCadenas (Cadena, SubCadena)
{
	var i = 0;
	var j = 0;
	var Result = 0;

	i = Cadena.length;
	j = SubCadena.length;
	if (j > 0)
	{	i -= j;
		while (i > 0)
		{	if (Cadena.substring (i, i + j) == SubCadena)
			{	Result++;
				i -= j;
			} else i--;
		}
	}
	return (Result);
}


function EmailCorrecto (Email)
{
	var filter  = /^([a-zA-Z0-9_\.\-])+\@(([a-zA-Z0-9\-])+\.)+([a-zA-Z0-9]{2,4})+$/;

	Email = Trim (Email);

	return (filter.test (Trim (Email)));
//	return ((Email.length > 5) &&
//                (CuentaSubCadenas (Email, "@") == 1) &&
//                (CuentaSubCadenas (Email, ".") > 0));
}


function GetParametro (Parametro, Defecto)
{
	var Parametros = window.location.search;
	var l = Parametros.length;
	var i = 1;
	var j = 1;
	var Result = null;

	Parametro = Parametro.toUpperCase ();
	if (l > 0 && Parametros.substr (0,1) == '?')
	{	while (i < l && Result == null)
		{	j = i;
			while (i < l && Parametros.substr (i, 1) != "=") i++;
			if (i < l)
			{	if (Parametros.substr (j, i - j).toUpperCase () == Parametro)
				{	j = ++i;
					while (i < l && Parametros.substr (i, 1) != "&") i++;
					Result = Parametros.substr (j, i - j);
				} else while (i < l && Parametros.substr (i, 1) != "&") i++;
			}
			i++;
		}
	};
	return (Result == null ? Defecto : Result);
}


function LTrim (Cadena)
{
	while (Cadena.length > 0 && (Cadena.substring (0, 1) == " " || Cadena.substring (0, 1) == "\t"))
		Cadena = Cadena.substring (1);
	return (Cadena);
}


function RTrim (Cadena)
{
	var i = Cadena.length;
	
	while (i > 0 && (Cadena.substring (i - 1, i) == " " || Cadena.substring (i - 1, i) == "\t"))
	{	Cadena = Cadena.substring (0, i - 1);
		i--;
	}
	return (Cadena);
}
	

function Trim (Cadena)
{
	if (typeof Cadena == 'undefined') return (''); else	return (LTrim (RTrim (Cadena)));
}