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added on-release

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svn: r18517
This commit is contained in:
Matthias Felleisen 2010-03-12 03:21:06 +00:00
parent 45da4cb3bc
commit b8a8ca533e
1 changed files with 25 additions and 10 deletions
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35
collects/teachpack/2htdp/scribblings/universe.scrbl
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@ -114,7 +114,7 @@ The step from simulations to interactive programs is relatively
@scheme[_create-image], as a handler for one kind of event: clock ticks. In
addition to clock ticks, @tech{world} programs can also deal with two
other kinds of events: keyboard events and mouse events. A keyboard event
is triggered when a computer user presses or releases a key on the
is triggered when a computer user presses a key on the
keyboard. Similarly, a mouse event is the movement of the mouse, a click
on a mouse button, the crossing of a boundary by a mouse movement, etc.
@ -154,13 +154,14 @@ The design of a world program demands that you come up with a data
@defform/subs[#:id big-bang
#:literals
(on-tick on-draw on-key on-mouse on-receive stop-when
(on-tick on-draw on-key on-release on-mouse on-receive stop-when
check-with register record? state name)
(big-bang state-expr clause ...)
([clause
(on-tick tick-expr)
(on-tick tick-expr rate-expr)
(on-key key-expr)
(on-release release-expr)
(on-mouse key-expr)
(on-draw draw-expr)
(on-draw draw-expr width-expr height-expr)
@ -209,8 +210,7 @@ tell DrScheme to call the @scheme[tick-expr] function on the current
world every time the clock ticks. The result of the call becomes the
current world. The clock ticks at the rate of @scheme[rate-expr].}}
@item{A @tech{KeyEvent} represents key board events, e.g., keys pressed or
released.
@item{A @tech{KeyEvent} represents key board events.
@deftech{KeyEvent} : @scheme[string?]
@ -238,7 +238,6 @@ Second, some keys have multiple-character string representations. Strings
@item{@scheme["right"] is the right arrow;}
@item{@scheme["up"] is the up arrow;}
@item{@scheme["down"] is the down arrow;}
@item{@scheme["release"] is the event of releasing a key;}
@item{@scheme["start"]}
@item{@scheme["cancel"]}
@item{@scheme["clear"]}
@ -311,10 +310,10 @@ Second, some keys have multiple-character string representations. Strings
@defproc[(key=? [x key-event?][y key-event?]) boolean?]{
compares two @tech{KeyEvent} for equality}
@defform[(on-key change-expr)
@defform[(on-key key-expr)
#:contracts
([change-expr (-> (unsyntax @tech{WorldState}) key-event? (unsyntax @tech{WorldState}))])]{
tell DrScheme to call @scheme[change-expr] function on the current world and a
([key-expr (-> (unsyntax @tech{WorldState}) key-event? (unsyntax @tech{WorldState}))])]{
tell DrScheme to call the @scheme[key-expr] function on the current world and a
@tech{KeyEvent} for every keystroke the user of the computer makes. The result
of the call becomes the current world.
@ -332,6 +331,16 @@ Second, some keys have multiple-character string representations. Strings
}
The omitted, auxiliary function @emph{world-go} is supposed to consume a
world and a number and produces a world.
@defform[(on-release release-expr)
#:contracts
([release-expr (-> (unsyntax @tech{WorldState}) key-event? (unsyntax @tech{WorldState}))])]{
tell DrScheme to call the @scheme[release-expr] function on the current world and a
@tech{KeyEvent} for every release event on the keyboard. A release event
occurs when a user presses the key and then releases it. The second argument
indicates which key has been released. The result of the function call
becomes the current world.
}
}
@item{ A @tech{MouseEvent} represents mouse events, e.g., mouse movements
@ -668,9 +677,15 @@ As mentioned, all event handlers may return @tech{WorldState}s or
}
@defform/none[#:literals (on-key)
(on-key change-expr)
(on-key key-expr)
#:contracts
([change-expr (-> (unsyntax @tech{WorldState}) key-event? (or/c (unsyntax @tech{WorldState}) package?))])]{
([key-expr (-> (unsyntax @tech{WorldState}) key-event? (or/c (unsyntax @tech{WorldState}) package?))])]{
}
@defform/none[#:literals (on-release)
(on-release release-expr)
#:contracts
([release-expr (-> (unsyntax @tech{WorldState}) key-event? (or/c (unsyntax @tech{WorldState}) package?))])]{
}
@defform/none[#:literals (on-mouse)