On Mar 19, 2012, at 3:10 PM, Roelof Wobben wrote:
> But the contents of color does not change so I get a error message.
> What is the racket way to change the value of a string.
That's not the problem. It's your error message, so you should be able to
figure out why it's happening. It has noth
ps. Your program's light function does NOT map Strings to Images. It maps World
to images, ASSUMING you have defined
;; World is ...
(probably string here but 1, 2, and 3 would work and so would many others).
On Mar 19, 2012, at 4:25 PM, Matthias Felleisen wrote:
>
> 1. Your program doe
1. Your program does NOT change a string. It changes the state of the traffic
light (or it tells drracket to keep track of a different state). The string
"rood" remains the same in eternity.
2. You're missing test cases, and if you had tested the program you would have
discovered it before ev
Oops... (still learning, Thanks Robby) ... New results run under Racket.exe:
(define (pythagorean-triple n)
(let loop-ab ([a 1] [b 2])
(define c (- n a b))
(cond [(right-triangle? a b c) (list a b c)]
[(>= a (ceiling (/ n 3))) '()]
[(<= c b) (loop-ab (add1 a) (+ a 2))
Hello,
I have to make a traffic-light which changes color after each tick of
the computer.
So I thought this would work :
;; String -> Image
;; given a state of a trafic-light display a circle of the given color
if it's a color of the traffic-light otherwise error
(define (light color)
(c
On Mon, Mar 19, 2012 at 14:14, Neil Van Dyke wrote:
> If you like to use tabs instead of windows in DrRacket 5.2.1, this is a
> very useful preference:
>
> "Preferences -> General -> Open files in separate tabs (not separate
> windows)"
>
It seems to me that this has been around long before 5.2.
Apologies if this is old news, but if you're running timing tests, be
sure to run them in 'racket', from a command-line, not in DrRacket.
DrRacket is doing lots of stuff at the same time as running your
program that can make measurements significantly less accurate.
Robby
On Mon, Mar 19, 2012 at
Hi again Rodolfo,
After a some mods, I ran several trials with n = 1 on my ancient laptop
and got the following results:
(define (pythagorean-triple n)
(define a-limit (ceiling (/ n 3)))
(let loop-ab ([a 1] [b 2])
(define c (- n a b))
(cond [(right-triangle? a b c) (list a b c)]
Fix was committed last Friday.
Kevin
Racket Users list:
http://lists.racket-lang.org/users
If you like to use tabs instead of windows in DrRacket 5.2.1, this is a
very useful preference:
"Preferences -> General -> Open files in separate tabs (not separate
windows)"
Then you can open additional files in tabs by selecting from the
pulldown filename widget on the left end of the tool
On Mon, Mar 19, 2012 at 04:35, Joe Gilray wrote:
> Thanks Rodolfo and Eli for the education, very elegant solutions.
>
> I really like the clever use of the "(and (right-triangle? a b c) (list a
> b c" idiom.
>
> I had to look up in-value... unfortunately the manual is a bit sparse
> there, b
Thanks Rodolfo and Eli for the education, very elegant solutions.
I really like the clever use of the "(and (right-triangle? a b c) (list a b
c" idiom.
I had to look up in-value... unfortunately the manual is a bit sparse
there, but I got the gift by running some examples... thanks.
After go
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