function its_a_digit(character) {

    var digit_characters = "0123456789";
    if (digit_characters.indexOf(character) == -1) {
        return false;
    }
    return true;
}
function its_integer(string_value) {
    for (var counter = 0; counter < string_value.length; counter++) {
        current_char = string_value.charAt(counter);
        if (!its_a_digit(current_char)) {
            return false;
        }
    }
    return true;
}

function check_integer(element, text){
	if(!its_integer(element.value)){
		alert(text+":\n"+element.value);
		element.value = "";
		element.focus();
		return;
	}
}

function Sami(name, code) {
    this.name = name
    this.code = code
}

var day_array1 = new Array(31);
var day_array2 = new Array(30);
var day_array3 = new Array(28);
var day_array = new Array();

function populate_array(k) {
switch(k){
	case 31:
	day_array = day_array1;
	break
	case 30:
	day_array = day_array2;
	break
	case 28:
	day_array = day_array3;
	break
}
for(counter = 0; counter < k; counter++){
	a = counter+1;
	day_array[counter] = new Sami(a, a);
}
}


function purge_characters(original_s, bad_characters) {
	original_string=original_s.value;
    var cleaned_string = ""
    
    for (var counter = 0; counter < original_string.length; counter++) {
        
        current_char = original_string.charAt(counter)
        
       if (bad_characters.indexOf(current_char) == -1) {
       
           cleaned_string += current_char
       }
    }
    return cleaned_string
}



function valid_email(email_address) {
    if (email_address.length < 5) {
        return false
    }
    at_location = email_address.indexOf("@")
    dot_location = email_address.lastIndexOf(".")
    
    if (at_location == -1 || dot_location == -1 || at_location > dot_location ) {
        return false
    }
    if (at_location == 0) {
        return false
    }
    if (dot_location - at_location < 2 ) {
        return false
    }
    if (email_address.length - dot_location < 2) {
        return false
    }
    return true
}