Hi IF,
I think this is what you want. You were right about the issue -- you were
consing onto the history list but then immediately throwing away the result
because it wasn't modifying the original history value.
#lang racket
(struct message (str sender recipient) #:transparent)
; This returns a list consisting of the message that we are sending
; out; followed by the message that the participant posted. It will
; be appended; to the history.
(define (say m str)
(displayln str)
(list (message str "me" "participant") m))
; start off with an empty history
(let loop ([history '()])
(display "Input: ")
(define input (message (read-line (current-input-port) 'any)
"participant" "me"))
(display "Chatbot: ")
(loop
(append
(match (message-str input)
[(regexp #rx"(?i:Hello,* world!)")
(say input "I would not know about the rest of the world, but I can
hear \
you just fine.")]
[(regexp #px"(?i:I( am|'m) learning how to program in Racket,*
world!)")
(say input "Racket is a great language, and it is lovely that you
are \
learning it, but does literally everyone need to know?")]
[(regexp #px".*,+\\s*world!")
(say input "Did the whole world really need to hear that?")]
; if your input is DEBUG then it will print out the history but not add to
it
["DEBUG" (pretty-print history) '()]
; if you type something unrecognized it will say so
[else (say input "I didn't understand that")])
history))
(loop))
PS Do I have the salutation right? Is it 'Hello, IF' or 'Hello, Karona'?
On Wed, Feb 24, 2021 at 6:21 PM IF Karona <karona...@gmail.com> wrote:
> 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 <gneun...@comcast.net>
> 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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