;; 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 (the string must be typed in quotations).
;; 
;(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 following function prompts the user 
;; for their full name and age and then prints the information to the
;; interactions window.

; 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 here because body of function is a printf and a local
    ;; statement
    (begin
      (printf "Please enter your full name in quotation marks:~%")
      (local
        [(define name (read))]
        ;; need a begin here 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))))))) 

;; This pattern of combining a printf expression before a read statement is 
;; known as "prompt and read".  The printf tells the user what entry is 
;; expected and the read statement reads the data.  The local and define
;; special forms are used to combine the printing and reading in a single
;; 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 statement must be used to store the
;; result of every read function.

;; There is a slightly shorter form of the local expression that allows
;; the definition of value holders within a function. This form is called
;; LET and is used in a similar way to local.

;; General pattern:  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))))))) 


;; 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.

; 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


(define guess-the-number
  (lambda ()
    (local
      ; 1. Generate and save the random number
      [(define CORRECT (add1 (random 100)))]
      ; 2. Give user instructions
      (begin
        (printf "Type a number between 1 and 100 and I'll give you hints~%")
        (printf "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
        (local
          [(define keep-guessing
             (lambda ()
               (begin
                 ; 4. Prompt for the user's guess
                 (printf "Make your guess now: ~%")
                 (local
                   ; 5. Read the guess.
                   [(define GUESS (read))]
                   ; 6. if guess equals the correct answer, give them feedback.
                   (if (= GUESS CORRECT) 
                       (printf "YOU GOT IT!! The number is ~a.~%" CORRECT)
                       ; 7. if guess is less than correct answer, tell user to
                       ;    guess higher
                       (if (> CORRECT GUESS)
                           (begin
                             (printf "Higher~%")
                             (keep-guessing))
                           ; 8. if guess is greater than correct answer, tell user to
                           ;    guess lower
                           (begin
                             (printf "Lower~%")
                             (keep-guessing))))))))]
          ; 9. Call inner guessing function
          (keep-guessing)))))) 

;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
;; 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

(define LIMIT 5)

; Function definition:
(define guess-the-number-5-tries
  (lambda ()
    (local
      ; 1. Generate and save the random number
      [(define CORRECT (add1 (random 100)))]
      ; 2. Give user instructions
      (begin
        (printf "Type a number between 1 and 100 and I'll give you hints~%")
        (printf "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
        (local
          [(define keep-guessing
             (lambda (acc)
               (begin
                 (if (> acc LIMIT)
                     (begin
                       (printf "You have already used all ~a guesses.~%" acc)
                       (printf "The number was ~a~%" CORRECT))
                     (begin
                       ; 4. Prompt for the user's guess
                       (printf "Make guess ~a now: ~%" acc) 
                       (local
                         ; 5. Read the guess.
                         [(define GUESS (read))]
                         ; 6. if guess equals the correct answer, give them feedback.
                         (if (= GUESS CORRECT) 
                             (printf "YOU GOT IT IN ~A GUESSES!! The number is ~a.~%" 
                                     (+ 1 acc) CORRECT)
                             ; 7. if guess is less than correct answer, tell user to
                             ;    guess higher
                             (if (> CORRECT GUESS)
                                 (begin
                                   (printf "That was guess ~a. Higher!~%" acc)
                                   (keep-guessing (add1 acc)))
                                 ; 8. if guess is greater than correct answer, tell user to
                                 ;    guess lower
                                 (begin
                                   (printf "That was guess ~a. Lower!~%" acc)
                                   (keep-guessing (add1 acc)))))))))))]
          ; 9. Call inner guessing function
          (keep-guessing 1))))))