Op 6-4-2012 9:20, Danny Yoo schreef:
On Friday, April 6, 2012, Roelof Wobben wrote:
Op 5-4-2012 20:29, Danny Yoo schreef:
I start with this :
aaaaa|
Concretely, what does the editor world value look like at this
point?
You're representing the state somewhat ambiguously. Can you
represent
the above in terms of (make-editor ... ...)?
Yes, (make-editor aaaaaa a """)
This can't be, as make-editor can only take two strings. The
structure definition of make editor is:
(define-struct editor (pre post))
Where both pre and post are both strings.
now someone press 3 times the left key.
So I have aa/aaa
rep has he value of aaaaa
s has the value of a
t has also the value of a.
You make the same conceptual mistake here. This representation does
not fit the shape of the structure definition.
Go back and make sure you understand the data definition. If you have
questions about it, please feel free to ask.
Oke,
Back to the beginning.
In the text is noted.
(define-struct
<http://docs.racket-lang.org/htdp-langs/beginner.html#%28form._%28%28lib._lang%2Fhtdp-beginner..rkt%29._define-struct%29%29>editor(prepost))
;Editor= (make-editorStringString)
;interp. (make-editorst)means the text in the editor is
;(string-append
<http://docs.racket-lang.org/htdp-langs/beginner.html#%28def._%28lib._htdp-beginner..rkt._lang%29._%28%28lib._lang%2Fhtdp-beginner..rkt%29._string-append%29%29>st)with
the cursor displayed between sand t
So for aaaaaaa| s has the value of aaaaa en t has the value of ""
For aaaa|aaaa s I think s has the value of aaaaa and t has the value of aaa
I have a idea.
If I use the length of the first string and I press one time on the
left-key then the new-length could be the old-one - 1. Then I could use
substring to cut that part away.
The t part I could say if it's empty substring ( s , (string-lenght s),
1) and if it's not empty use a string-append.
Am I on the right track ?
Roelof
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