Thank you!
I can get the code that follows to run, but the chatbot never replies. I
surmise this is because lists are not mutable.
With the background I have the most obvious way forward would be to use an
array instead of a list, but that does not strike me as the best approach
to take while trying to learn functional programming.
Is there a better way through this?
;example.rkt
#lang racket
(require racket/match)
(struct message (str sender recipient))
(define chat-history (list (message "" "" "")))
(define (say m)
(cons m chat-history))
(define (log m)
(cons m chat-history))
(let loop ()
(display "Input: ")
(define input (message (read-line (current-input-port) 'any)
"participant" "me"))
(define str (message-str input))
(log input)
(cond
[(regexp-match #px"(?i:Hello,* world!)" str)
(say (message "I would not know about the rest of the world, but I can
hear \
you just fine." "me" "participant"))]
[(regexp-match #px"(?i:I( am|'m) learning how to program in Racket,*
world!)" str)
(say (message "Racket is a great language, and it is lovely that you
are \
learning it, but does literally everyone need to know?" "me"
"participant"))]
[(regexp-match #px".*,+\\s*world!" str)
(say (message "Did the whole world really need to hear that?" "me"
"participant"))]
[else (say (message "Did you really just say something without
addressing the \
world? I am so proud of you! :,)" "me" "participant"))])
(define head (first chat-history))
(define response (message-str head))
(printf "Chatbot: ~a\n" response)
(loop))
On Wed, Feb 24, 2021 at 3:11 PM George Neuner <[email protected]> wrote:
>
> Hi,
>
> Presumably you are using 'head' to get the first element of a list.
> However, there is no function 'head' for lists.
> see: https://docs.racket-lang.org/reference/pairs.html
>
> Try using 'first' and 'rest' instead of 'head' and 'tail'.
>
> George
>
>
> On 2/24/2021 3:55 PM, IF Karona wrote:
>
> Hi everyone,
>
> After trying to implement some changes Sage suggested (all errors are my
> own), I am now encountering the following message (courtesy of DrRacket):
>
> "head: unbound identifier in: head"
>
> Could someone help me find a fix?
>
> As before, I welcome suggestions on how to better do this the functional
> programming way.
>
> Karona
>
> ;example.rkt
>
> #lang racket
>
> (require racket/match)
>
> (struct message (str sender recipient))
>
> (define (say chat-history m)
> (cons m
> chat-history))
>
> (define (log chat-history m)
> (cons m
> chat-history))
>
> (let loop ()
> (display "Input: ")
> (define input (message (read-line (current-input-port) 'any)
> "participant" "me"))
> (define str (message-str input))
> (log chat-history input)
>
> (cond
>
> [(regexp-match #px"(?i:Hello,* world!)" str)
> (say chat-history (message "I would not know about the rest of the
> world, but I can hear \
> you just fine." "me" "participant" "me" "participant"))]
>
> [(regexp-match #px"(?i:I( am|'m) learning how to program in Racket,*
> world!)" str)
> (say chat-history (message "Racket is a great language, and it is
> lovely that you are \
> learning it, but does literally everyone need to know?" "me"
> "participant"))]
>
> [(regexp-match #px".*,+\\s*world!" str)
> (say chat-history (message "Did the whole world really need to hear
> that?" "me" "participant"))]
>
> [else (say chat-history (message "Did you really just say something
> without addressing the \
> world? I am so proud of you! :,)" "me" "participant"))])
>
> (define hd (head chat-history))
> (define s (message-str hd))
> (printf "Chatbot: ~a\n" s)
> (loop)) --
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