/*
function isEmail(s)
{   
  if (isWhitespace(s)) return false
  if(s.indexOf(" ")>0) return false;
  var i = 1;
  var sLength = s.length;
  if (s.indexOf(".")==sLength) return false;
  if (s.indexOf(".")<=0) return false;
  if (s.indexOf("@")!=s.lastIndexOf("@")) return false;

  while ((i < sLength) && (s.charAt(i) != "@"))
  { i++
  }

  if ((i >= sLength) || (s.charAt(i) != "@")) return false;
  else i += 2;

  while ((i < sLength) && (s.charAt(i) != "."))
  { i++
  }

  if ((i >= sLength - 1) || (s.charAt(i) != ".")) return false;
  else return true;
}
*/
function isEmail(s)
{   
  if (isWhitespace(s)) return false
  if(s.indexOf(" ")>0) return false;
  var i = 1;
  var sLength = s.length;
  if ((s.indexOf(".")==sLength)||(s.lastIndexOf(".")==sLength)) return false;
  if (s.indexOf(".")<=0) return false;
  if (s.indexOf("@")!=s.lastIndexOf("@")) return false;

  while ((i < sLength) && (s.charAt(i) != "@"))
  { i++
  }

  if ((i >= sLength) || (s.charAt(i) != "@")) return false;
  else i += 2;

  while ((i < sLength) && (s.charAt(i) != "."))
  { i++
  }

  if ((i >= sLength - 1) || (s.charAt(i) != ".")) 
  	return false;
  else 
	{
		username=s.substring(0,s.indexOf("@"));
		domain=s.substring(s.indexOf("@")+1,s.length);
		usernames="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
		domains="ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_.";
		ULength=username.length;
		DLength=domains.length;		
		k=0
		m=0
		while (k < ULength) 
		  { 
		 	if (usernames.indexOf(username.charAt(k).toString())<0)
				{
					 return false;
				}
		  	k++
		  }
		 while (m < DLength) 
		  { 
		 	if (domains.indexOf(domain.charAt(m).toString())<0 )
				{
					 return false;
				}
		  	m++
		  }
	}
	
  return true;
}

function isEmpty(s)
{   
	return ((s == null) || (s.length == 0))
}

function isWhitespace (s)
{   
	var whitespace = " \t\n\r";
	var i;

  if (isEmpty(s)) return true;
  for (i = 0; i < s.length; i++)
  {   
    var c = s.charAt(i);
    if (whitespace.indexOf(c) == -1) return false;
  }
  return true;
}