CALCULATOR DRRACKET.rkt~

#lang racket/gui

; Arithmetic operations
(define (add a b) (+ a b))
(define (subtract a b) (- a b))
(define (multiply a b) (* a b))
(define (divide a b) (if (= b 0) "Error" (/ a b)))

; Function to parse and evaluate the expression
(define (parse-and-eval input)
  (define tokens (string-split input))
  (if (= (length tokens) 3)
      (let ([val1 (string->number (list-ref tokens 0))]
            [op (list-ref tokens 1)]
            [val2 (string->number (list-ref tokens 2))])
        (cond
          [(and (number? val1) (number? val2))
           (case op
             [("+") (add val1 val2)]
             [("-") (subtract val1 val2)]
             [("*") (multiply val1 val2)]
             [("/") (divide val1 val2)]
             [else "Error"])]
          [else "Error"]))
      "Error"))

; GUI components
(define FRAME (new frame% [label "Calculator"]
                   [width 300]
                   [height 400]))

(define DISPLAY (new text-field% [parent FRAME]
                     [label ""]
                     [min-width 280]
                     [min-height 50]))

(define (button-callback button-label)
  (lambda (button event)
    (cond
      [(string=? button-label "=")
       (let ([result (parse-and-eval (send DISPLAY get-value))])
         (send DISPLAY set-value
               (if (number? result)
                   (number->string result)
                   result)))]
      [(string=? button-label "C")
       (send DISPLAY set-value "")]
      [else
       (send DISPLAY set-value
             (string-append (send DISPLAY get-value) " " button-label " "))])))

(define BUTTONS
  '("1" "2" "3" "+" "4" "5" "6" "-" "7" "8" "9" "*" "C" "0" "=" "/"))

(define PANEL (new vertical-panel% [parent FRAME]
                   [spacing 10]))

(define (make-button-row panel row-buttons)
  (define h-panel (new horizontal-panel% [parent panel] [spacing 10]))
  (for ([btn (in-list row-buttons)])
    (new button%
         [parent h-panel]
         [label btn]
         [min-width 50]
         [min-height 50]
         [callback (button-callback btn)])))

(make-button-row PANEL '("7" "8" "9" "/"))
(make-button-row PANEL '("4" "5" "6" "*"))
(make-button-row PANEL '("1" "2" "3" "-"))
(make-button-row PANEL '("C" "0" "=" "+"))

(send FRAME show #t)

; Test function for parse-and-eval
(define (test-parse-and-eval)
  (define tests '(("3 + 2" 5)
                  ("10 - 4" 6)
                  ("7 * 3" 21)
                  ("16 / 4" 4)
                  ("5 / 0" "Error")
                  ("abc + 1" "Error")
                  ("1 + 2 + 3" "Error")  ; Invalid format
                  ("+" "Error")          ; Missing operands
                  ("1 2 +" "Error")))    ; Incorrect format

  (for ([test (in-list tests)])
    (define input (first test))
    (define expected (second test))
    (define result (parse-and-eval input))
    (if (equal? result expected)
        (printf "Test passed for input: ~a\n" input)
        (printf "Test failed for input: ~a. Expected: ~a, but got: ~a\n"
                input expected result))))

; Run tests
(test-parse-and-eval)