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#lang racket/base
(require web-server/servlet)
(define (extract-number req)
(string->number
(extract-binding/single
'number
(request-bindings req))))
; build-request-page : str str -> response
(define (build-request-page which-number k-url)
(response/xexpr
`(html (head (title "Enter a Number to Add"))
(body ([bgcolor "white"])
(form ([action ,k-url] [method "post"])
"Enter the " ,which-number " number to add: "
(input ([type "text"] [name "number"] [value ""]))
(input ([type "submit"] [name "enter"] [value "Enter"])))))))
(define (get-first req)
(build-request-page "First" (add-url get-second)))
(define (get-second req)
(define fst (extract-number req))
(build-request-page "Second" (add-url display-sum fst)))
(define (display-sum req fst)
(define snd (extract-number req))
(response/xexpr
`(html (head (title "Sum"))
(body ([bgcolor "white"])
(p "The answer is "
,(number->string (+ fst snd)))))))
(define-values (start add-url)
(dispatch-rules
[("get-second") get-second]
[("display-sum" (integer-arg)) display-sum]
[else get-first]))
(serve/dispatch start)
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