readme.txt -- for exps-have-numbers-ss

readme.txt -- for exps-have-numbers-ss

THE TASK

In this task modify SpreadSheet.java so that numbers can be directly
entered as expression operands in formulas, freely mixed with cell
references.

For this task, a number is defined as a character string
that can be interpreted as a double value using Java's
Scanner::nextDouble() method WITH THE EXCEPTIONS that you may assume



  1. Operator characters (in particular "+" and "-") are not present,
     so all numbers are non-negative, and there are no embedded
     operators, as in 1.3e-6 and 2e+5.
REED'S NOTES:
1) Info on Operator characters: https://docs.oracle.com/javase/tutorial/java/nutsandbolts/opsummary.html
2) non-negative: either positive or equal to zero.
3) embedded operators: Translation?

  2. SignedNonNumbers such as NaN and Infinity are not present.
REED'S NOTES:
1) SignedNonNumbers: Translation?
2) NaN: not a number, a numeric data type value representing an undefined or
unrepresentable value(especially in floating-point calculations).

Video demonstrations of a solution for this task are available.
    1. During the exam: as exps-have-numbers-ss.html in the "Solution Demonstration Videos"
       folder on the desktop in the exam delivery environment.
    2. During exam preparation, outside the exam environment.
       https://s3-us-west-2.amazonaws.com/proxor-video/video/exps-have-numbers-ss-transcoded.mp4

REED'S NOTES:

***SCANNER***

1) Simple text scanner, can parse primitive types & strings using regular expressions.

2) Scanner breaks input into tokens using delimiter pattern(default matches whitespace).

3) The resulting tokens may then be converted into values of different types using the various *NEXT METHODS*.

EX:
     // allows a user to read a number from System.in
     Scanner sc = new Scanner(System.in);
     int i = sc.nextInt();

 EX:
      // allows long types to be assigned from entries in a file myNumbers
      Scanner sc = new Scanner(new File("myNumbers"));
      while (sc.hasNextLong()) {
          long aLong = sc.nextLong();
      }

4) Scanner can use delimiters other than whitespace.

EX:
      // reads several items in from a string:

     String input = "1 fish 2 fish red fish blue fish";
     Scanner s = new Scanner(input).useDelimiter("\\s*fish\\s*");
     System.out.println(s.nextInt());
     System.out.println(s.nextInt());
     System.out.println(s.next());
     System.out.println(s.next());
     s.close();

Output:

     1
     2
     red
     blue

5) Same output can be generated with code bellow,
uses regular expression to parse all four tokens at once:

EX:
     String input = "1 fish 2 fish red fish blue fish";
     Scanner s = new Scanner(input);
     s.findInLine("(\\d+) fish (\\d+) fish (\\w+) fish (\\w+)");
     MatchResult result = s.match();
     for (int i=1; i<=result.groupCount(); i++)
         System.out.println(result.group(i));
     s.close();

6) more on Scanner:

http://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html

REED'S NOTES:

***NEXTDOUBLE()***

1) Scans the next token of the input as a double.

2) Returns the double scanned from the input.

3) will throw InputMismatchException if the next token cannot
be translated into a valid double value.
If the translation is successful,
the scanner advances past the input that matched.

4)

EX:

public static void main(String[] args) {

   String s = "Hello World! 3 + 3.0 = 6 true";

   // create a new scanner with the specified String Object
   Scanner scanner = new Scanner(s);

   // use US locale to be able to identify doubles in the string
   scanner.useLocale(Locale.US);

   // find the next double token and print it
   // loop for the whole scanner
   while (scanner.hasNext()) {

   // if the next is a double, print found and the double
   if (scanner.hasNextDouble()) {
   System.out.println("Found :" + scanner.nextDouble());
   }

   // if a double is not found, print "Not Found" and the token
   System.out.println("Not Found :" + scanner.next());
   }

   // close the scanner
   scanner.close();
   }

OUTPUT:

Not Found :Hello
Not Found :World!
Found :3.0
Not Found :+
Found :3.0
Not Found :=
Found :6.0
Not Found :true


5) more on nextDouble():

http://docs.oracle.com/javase/7/docs/api/java/util/Scanner.html#nextDouble()

REED'S NOTES:

***EXCEPTIONS you may assume***

1) InputMismatchException -- if the next token does not match the Float regular expression, or is out of range

2) NoSuchElementException -- if the input is exhausted

3) IllegalStateException -- if this scanner is closed