;; CS101, Spring 2013 
;; Lecture #13    
;; 
;  The READ function:
;  
;  read is a zero-parameter function that displays a box for entry in   
;  the interactions window and returns whatever is typed (up to, but
;  not including the first space) as a quoted symbol, a number, or a 
;  string (a string to be read must be typed in quotations and can 
;  include the space character).
;  


;(read)

; 
;  read is used to get input from the user of the program and should 
;  always be used after a printf that prompts the user for the data
;  to be read.  
; 
;  For example, the function get-name-and-age below prompts the user for 
;  their full name and age and then prints the information in the 
;  interactions window.
;  
;  General pattern for reading input:  begin->printf->local->read
;  


; Contract: (get-name-and-age) -> void; side-effect printing
; Header:   (define get-name-and-age (lambda () ...))
; Purpose:  Prompt for and read a person's name and age and echo back the
;           information in a printf statement.
; Pre-function tests: Not possible due to void return type

; Function definition:
(define get-name-and-age
  (lambda ()
    
    ;; need a begin below because body of function contains both 
    ;; a printf and a local statement
    (begin
      
      (printf "Please enter your full name in quotation marks:~%")
      
      (local
        [(define name (read))]
        
        ;; need a begin below because a printf will precede the next local
        ;; statement
        (begin
          
          (printf "~%~%Please enter your age:~%")
          
          (local
            [(define age (read))]
            
            ;; print the result of the two read statements
            (printf "~%~%Name: ~a, Age: ~a~%~%" name age)))))))  

;  
;  There is a slightly shorter form of the local expression that allows   
;  the definition of constants within a function. This form is called
;  LET and is used in a similar way to local.
;  
;  General pattern for reading input:  begin->printf->let->read
;  


; Contract: (get-name-and-age-let) -> void; side-effect printing
; Header:   (define get-name-and-age-let (lambda () ...))
; Purpose:  Prompt for and read a person's name and age and echo back the
;           information in a printf statement.
; Pre-function tests: Not possible due to void return type

; Function definition:
(define get-name-and-age-let
  (lambda ()
    ;; need a begin here because body of function is a printf and a let
    ;; statement
    (begin
      
      (printf "Please enter your full name in quotation marks:~%")
      
      (let [(name (read))]
        ;; need a begin here because a printf will precede the next local
        ;; statement
        (begin
          
          (printf "~%~%Please enter your age:~%")
          
          (let [(age (read))]
            ;; print the result of the two read statements
            (printf "~%~%Name: ~a, Age: ~a~%~%" name age))))))) 



;  
;  The pattern of combining a printf expression before a read statement
;  as shown in the two functions above is known as the "prompt and read"
;  pattern.
;  
;  The printf tells the user what entry is expected and the read statement 
;  inside a local or let saves the data for use in the body of the function. 
; 
;  Advanced Student Language does not allow a define statement to be used
;  inside a function without being preceded by a local special form.  This 
;  means that a new local or let statement must be used to store the result 
;  of every separate read function that is done in response to a single 
;  prompt.
;  


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; CLASS EXERCISE 1:
;;
;; Write a function to play Guess The Number with the computer.  The game
;; goes as follows:  The computer generates a random number between 1 and
;; 100 and then asks the user to guess the number.  The program should 
;; allow the user to continue guessing numbers until they guess the correct
;; number.  If the guess is too low, the computer prints "Higher", and if
;; the guess is too high, the computer prints "Lower".  The algorithm is 
;; given below.

; Contract: (guess-the-number) -> void ; side-effect printing
; Header:   (define guess-the-number (lambda () ... )) 
; Purpose:  Guess the number generated at random by the computer.
; Pre-function tests: None possible due to only side effect printing

; Function definition:
;(define guess-the-number
;  (lambda ()
      ; 1. Generate and save the random number.

      ; 2. Give user instructions:
      ;    "Type a number between 1 and 100 and I'll give you hints"
      ;    "to let you know if the correct answer is higher or lower."

      ; 3. Define a local function to loop until the correct answer is guessed.

      ; 4.     Prompt for the user's guess:
      ;        "Make your guess now:"
 
      ; 5.     Read the guess.
 
      ; 6.     if guess equals the correct answer, give them feedback:
      ;        "YOU GOT IT!! The number is <the number generated in step 1>"

      ; 7.     if guess is less than correct answer, tell user to guess higher
      ;        and call local function recursively.

      ; 8.     if guess is greater than correct answer, tell user to guess lower
      ;        and call local function recursively.

      ; 9. Call local function defined in step 3.


;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; CLASS EXERCISE 2:
;;
;; Change the guess-the-number function so that it counts the number of 
;; guesses the user makes and stops them at guess 5.  Call the function 
;; guess-the-number-5-tries.
  
; Contract: (guess-the-number-5-tries) -> void ; side-effect printing
; Header:   (define guess-the-number-5-tries (lambda () ... )) 
; Purpose:  Guess the number generated at random by the computer. Only
;           LIMIT number of guesses are allowed.
; Pre-function tests: None possible due to only side effect printing

; Function definition:
;(define guess-the-number-5-tries
;  (lambda ()