Op 18-4-2012 12:32, Pierpaolo Bernardi schreef:
On Wed, Apr 18, 2012 at 11:17, Roelof Wobben<r.wob...@home.nl> wrote:
Hello,
I try to make a function which controls the key-events.
The function does only have to react on backspace , left , right .
Give no reaction on tab , rubout or the other keys with a length more then
1.
When given another key with length 1 it has to insert the key.
So i thought this would work :
(define (edit e k)
(cond
[ (and(key=? "right" k) (> (string-length (editor-post e)) 0))
(make-editor(string-append (editor-pre e) (string-first (editor-post e) ))
(string-rest (editor-post e) ))]
[ (and(key=? "left" k) (> (string-length (editor-pre e)) 0))
(make-editor ( string-remove-last (editor-pre e) ) (string-append
(string-last(editor-pre e)) (editor-post e)))]
[ (and (key=? "\b" k) (> (string-length (editor-pre e)) 0))
(make-editor (string-remove-last (editor-pre e)) (editor-post e))]
[ (not ( or (key=? "\t" k ) (key=? "\u007F" k) (key=? "right" k))) (
string-append (editor-pre e) k)]
[else e]
))
but now when someone press the right-key the first get executed but also the
not rule.
I thought that cond works if one rule is true the other gets ignored. But it
looks like that's not true.
Now my question is : how can I take care that all the other key's with
length 1 except backspace, tab, and rubout get's executed ?
maybe:
(define (edit e k)
(cond ((key=? "right" k)
(if (zero? (string-length (editor-post e)))
e
<create an updated new editor>))
((key=? "left" k)
(if (zero? (string-length (editor-pre e)))
e
<create an updated new editor>))
...
))
?
oke, but why string-length 0 . In my opinion the string-length of the
key is 1 or more then 1.
So I thought of this :
(define (edit e k)
(cond
[ (and(key=? "right" k) (> (string-length (editor-post e)) 0))
(make-editor(string-append (editor-pre e) (string-first (editor-post e) ))
(string-rest (editor-post e) ))]
[ (and(key=? "left" k) (> (string-length (editor-pre e)) 0))
(make-editor ( string-remove-last (editor-pre e) ) (string-append
(string-last(editor-pre e)) (editor-post e)))]
[ (and (>(string-length k)1) (not (or(key=? "left" k) (key=? "right" k))) e
[ (and (key=? "\b" k) (> (string-length (editor-pre e)) 0))
(make-editor (string-remove-last (editor-pre e)) (editor-post e))]
[ (and (equal (string-length k)1) (not ( or (key=? "\t" k ) (key=? "\u007F" k)
(key=? "bs" k))) (
string-append (editor-pre e) k)]
[else e]
))
This is not tested and can have bugs.
Roelof
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