function isListaEmpty ( l ) {
	return( (l.selectedIndex == -1) );
	}
function isEmpty( s ) {
    return( (s == null) || (s.length == 0) );
	}
function isLetter( c ) {
    return( ((c >= "a") && (c <= "z")) || ((c >= "A") && (c <= "Z")) )
	}
function isDigit(c) {
    return( ((c >= "0") && (c <= "9")) || c == ".")
	}
function isAlpha( strX ) {
    for ( var i=0; i < strX.length; i++ ) {
        if ( isLetter( strX.charAt(i) ) )
            return( true );
    	}
    return( false );
	}
function isNumber( intX ) {
    for ( var i=0; i < intX.length; i++ ) {
        if ( ! isDigit( intX.charAt(i) ) )
            return( false );
    	}
    return( true );
	}
function devuelve_numero(intX) {
	if ( isNumber( intX ) )
		return( intX );
	else
		var rr = 0;
		return( rr );
	}
function modulo11( rut, digVer ) {
    var mul = 2;
    var sum = 0;
    for ( var i=rut.length-1; i>=0; i-- ){
        sum += rut.charAt(i)*mul;
        mul++;
        if ( mul > 7 )
            mul = 2;
    	}
    var dig = sum % 11;
    dig = 11 - dig;
    if ( dig == 11 )
        dig = 0;
    else if ( dig == 10 )
        dig = "K";
    return ( digVer.toUpperCase() == dig );
	}

function isDate(fecha)
{ 
   if (fecha)
   {  
      borrar = fecha;
      if ((fecha.substr(2,1) == "-") && (fecha.substr(5,1) == "-"))
      {      
         for (i=0; i<10; i++)
	     {	
            if (((fecha.substr(i,1)<0) || (fecha.substr(i,1)>9)) && (i != 2) && (i != 5))
			{
               borrar = '-';
               break;  
			}  
         }
	     if (borrar)
	     { 
	        a = fecha.substr(6,4);
		    m = fecha.substr(3,2);
		    d = fecha.substr(0,2);
		    if((a < 1900) || (a > 2050) || (m < 1) || (m > 12) || (d < 1) || (d > 31))
		       borrar = '-';
		    else
		    {
		       if((a%4 != 0) && (m == 2) && (d > 28))	   
		          borrar = '-'; // Aņo no viciesto y es febrero y el dia es mayor a 28
			   else	
			   {
		          if ((((m == 4) || (m == 6) || (m == 9) || (m==11)) && (d>30)) || ((m==2) && (d>29)))
			         borrar = '-';	      				  	 
			   } 
		    } 
         } 
      }
	  else
	     borrar = '-';
	  if (borrar == '-')
	     alert('Fecha incorrecta...');
   }
}

function check_email(address){
	if ((address == "") || (address.indexOf ('@') == -1) || (address.indexOf ('.') == -1))
		return false;
	else
		return true;
	}