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porting guide, please propagate to release

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svn: r17759
This commit is contained in:
Matthias Felleisen 2010-01-20 09:30:31 +00:00
parent ef922d8e0d
commit 6220900756
2 changed files with 49 additions and 27 deletions
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70
collects/teachpack/2htdp/scribblings/port.scrbl
View File

@ -191,33 +191,55 @@ The most important change concerns the lines that launch the world program:
the old names but shorter.
@;{
key events and mouse events are string: use key=? and mouse=?
The other big change concerns key event handling and mouse event
handling. The respective handlers no longer accept symbols and chars but
strings only. Here is the first key event handler from the documentation
of the world teachpack:
stuff from Todd:
@port[
@schemeblock[
(define (change w a-key-event)
(cond
[(key=? a-key-event 'left)
(world-go w -DELTA)]
[(key=? a-key-event 'right)
(world-go w +DELTA)]
[(char? a-key-event)
w]
[(key=? a-key-event 'up)
(world-go w -DELTA)]
[(key=? a-key-event 'down)
(world-go w +DELTA)]
[else
w]))]
@; ---------------------------------
@schemeblock[
(define (change w a-key-event)
(cond
[(key=? a-key-event "left")
(world-go w -DELTA)]
[(key=? a-key-event "right")
(world-go w +DELTA)]
[(= (string-length a-key-event) 1)
w]
[(key=? a-key-event "up")
(world-go w -DELTA)]
[(key=? a-key-event "down")
(world-go w +DELTA)]
[else
w]))
]]
Note how the @scheme[char?] clause changed. Since all chars are now
represented as strings containing one ``letter'', the program on the right
just checks the length of the string. Otherwise, we simply change all
symbols into strings.
I'm not actually worried about me--I try to stay up to date, and I
teach three intro classes, so enough of my time is devoted to the HtDP
languages that I can stay on top of things. I'm worried about people
like Renee Ciezki in Arizona who pushes other teachers in her county
to use HtDP only to discover that the lessons she's given them to use
don't quite work anymore. At least she emails and asks what's going
on--I'm afraid other people just throw up their hands in frustration.
And it's not just that one change to go from world to universe--key
events became strings instead of symbols, for example, and there are a
number of other small changes. Having a checklist that explains how to
get from X to Y would make the transition less complicated.
Also, being unable to show previous student projects as examples is a
major downer. It's incredibly motivational to current students to see
what previous students have done. Porting five or six old projects to
the new version can eat up a couple of hours if you have to run them
and just correct errors. That's not horrible unless you don't have a
couple of hours to do it.
}
If you ever recorded your programs' work via an animated gif, you can still
do so. Instead of adding a fifth argument to @scheme[big-bang], however,
you will need to add a clause of the shape @scheme[(record? x)].
Finally, the universe teachpack implements a richer functionality than the
world teachpack.
@; -----------------------------------------------------------------------------
@section{Porting Image Programs}

6
collects/teachpack/2htdp/scribblings/universe.scrbl
View File

@ -430,11 +430,11 @@ All @tech{MouseEvent}s are represented via strings:
@item{
@defproc[(stop-with [w (unsyntax @tech{WorldState})]) (stop-with (unsyntax @tech{WorldState}))]{signals to
DrScheme that the current world program should shut down. That is, any
@defstruct[stop-with ([w (unsyntax @tech{WorldState})])]{signals to
DrScheme that the world program should shut down. That is, any
handler may return @scheme[(stop-with w)] provided @scheme[w] is a
@tech{WorldState}. If it does, the state of the world becomes @scheme[w]
but @scheme[big-bang] will close down all event handling.}
and @scheme[big-bang] will close down all event handling.}
}