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fix up some cross references

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Matthew Flatt 2013-02-16 09:49:24 -07:00
parent 9b04aef0f8
commit 83900f0d20
1 changed files with 26 additions and 23 deletions
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49
collects/teachpack/2htdp/scribblings/universe.scrbl
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@ -21,6 +21,9 @@
#;(map flow* (map car stuff))
#;(map flow* (map cadr stuff))))))
@(define WorldState @tech[#:tag-prefixes '("world")]{WorldState})
@(define S-expression @tech[#:tag-prefixes '("universe")]{S-expression})
@; -----------------------------------------------------------------------------
@teachpack["universe"]{Worlds and the Universe}
@ -158,7 +161,7 @@ The following picture provides an intuitive overview of the workings of a
@image["nuworld.png"]
The @racket[big-bang] form installs @racket[World_0] as the initial @tech{WorldState}.w
The @racket[big-bang] form installs @racket[World_0] as the initial @tech{WorldState}.
The handlers @racket[tock], @racket[react], and @racket[click] transform
one world into another one; each time an event is handled, @racket[done] is
used to check whether the world is final, in which case the program is
@ -171,7 +174,7 @@ The design of a world program demands that you come up with a data
definition of all possible states. We use @tech{WorldState} to refer to
this collection of data, using a capital W to distinguish it from the
program. In principle, there are no constraints on this data
definition though it mustn't be an instance of the @tech{Package}
definition though it mustn't be an instance of the @tech[#:tag-prefixes '("universe")]{Package}
structure (see below). You can even keep it implicit, even if this
violates the Design Recipe.
@ -249,7 +252,7 @@ now.
All remaining clauses are optional. To introduce them, we need one more
data definition:
@deftech{HandlerResult} : is a synonym for @racket[WorldState] until @secref[#:tag-prefixes '("universe")]{world2}
@deftech{HandlerResult} : is a synonym for @tech{WorldState} until @secref[#:tag-prefixes '("universe")]{world2}
@itemize[
@ -824,7 +827,7 @@ Simulating any dynamic behavior via a @tech{world} program demands two
different activities. First, we must tease out those portions of our
domain that change over time or in reaction to actions, and we must
develop a data representation for this information. This is what we call
@tech{WorldState}. Keep in
@|WorldState|. Keep in
mind that a good data definition makes it easy for readers to map data to
information in the real world and vice versa. For all others aspects of
the world, we use global constants, including graphical or visual
@ -835,7 +838,7 @@ Second, we must translate the actions in our domain---the arrows in the
teachpack can deal with. Once we have decided to use the passing of time
for one aspect, key presses for another, and mouse movements for a third,
we must develop functions that map the current state of the
world---represented as data from @tech{WorldState}---into the next state of the
world---represented as data from @|WorldState|---into the next state of the
world. Put differently, we have just created a wish list with three
handler functions that have the following general contract and purpose
statements:
@ -917,14 +920,14 @@ Note the @racket[list] clause includes @racket[empty] of course.
Each world-producing callback in a world program---those for handling clock
tick events, keyboard events, and mouse events---may produce a
@tech{Package} in addition to just a @tech{WorldState}:
@tech{Package} in addition to just a @|WorldState|:
@deftech{HandlerResult} is one of the following:
@itemize[
@item{@tech[#:tag-prefixes '("world")]{WorldState}}
@item{@|WorldState|}
@item{@tech{Package}}
]
where @deftech{Package} represents a pair consisting of a @tech{WorldState}
where @deftech{Package} represents a pair consisting of a @|WorldState|
and a message from a @tech{world} program to the @tech{server}. Because
programs send messages via @tech{Package}, the teachpack does not
provide the selectors for the structure, only the constructor and a
@ -934,14 +937,14 @@ Each world-producing callback in a world program---those for handling clock
determine whether @racket[x] is a @tech{Package}.}
@defproc[(make-package [w any/c][m sexp?]) package?]{
create a @tech{Package} from a @tech{WorldState} and an @tech{S-expression}.}
create a @tech{Package} from a @|WorldState| and an @tech{S-expression}.}
Recall that event handlers return a @tech[#:tag-prefixes'("universe")]{HandlerResult},
and we have just refined this data definition. Hence, each handler may return either a
@tech{WorldState} or a @tech{Package}. If an event handler produces a @tech{Package},
@|WorldState| or a @tech{Package}. If an event handler produces a @tech{Package},
the content of the world field becomes the next world and the message field specifies
what the world sends to the universe. This distinction also explains why the data
definition for @tech{WorldState} may not include a @tech{Package}.
definition for @|WorldState| may not include a @tech{Package}.
@subsection{Connecting with the Universe}
@ -996,14 +999,14 @@ The @racket[on-receive] clause of a @racket[big-bang] specifies the event handle
@defform[(on-receive receive-expr)
#:contracts
([receive-expr (-> (unsyntax @tech{WorldState}) sexp? (unsyntax @tech[#:tag-prefixes '("universe")]{HandlerResult}))])]{
([receive-expr (-> (unsyntax @|WorldState|) sexp? (unsyntax @tech[#:tag-prefixes '("universe")]{HandlerResult}))])]{
tells DrRacket to call @racket[receive-expr] for every message receipt, on the current
@tech{WorldState} and the received message. The result of the call becomes the current
@tech{WorldState}.
@|WorldState| and the received message. The result of the call becomes the current
@|WorldState|.
Because @racket[receive-expr] is (or evaluates to) a world-transforming
function, it too can produce a @tech{Package} instead of just a
@tech{WorldState}. If the result is a @tech{Package}, its message content is
@|WorldState|. If the result is a @tech{Package}, its message content is
sent to the @tech{server}.}
The diagram below summarizes the extensions of this section in graphical form.
@ -1015,9 +1018,9 @@ A registered world program may send a message to the universe server
message is transmitted to the server, which may forward it to some
other world program as given or in some massaged form. The arrival of a
message is just another event that a world program must deal with. Like
all other event handlers @emph{receive} accepts a @tech{WorldState} and some
all other event handlers @emph{receive} accepts a @|WorldState| and some
auxiliary arguments (a message in this case) and produces a
@tech{WorldState} or a @tech{Package}.
@|WorldState| or a @tech{Package}.
When messages are sent from any of the worlds to the universe or vice versa,
there is no need for the sender and receiver to synchronize. Indeed, a sender
@ -1125,7 +1128,7 @@ teachpack provides only a predicate and a constructor for these structures:
determines whether @racket[x] is a @emph{mail}.}
@defproc[(make-mail [to iworld?] [content sexp?]) mail?]{
creates a @emph{mail} from a @emph{iworld} and an @tech{S-expression}.}
creates a @emph{mail} from a @emph{iworld} and an @|S-expression|.}
}
]
@ -1420,9 +1423,9 @@ From the perspective of the @tech{universe}, the design of a protocol is
about the design of data representations for tracking universe information
in the server and the participating worlds and the design of a data
representation for messages. As for the latter, we know that they must be
@tech{S-expression}s, but usually @tech{world} programs don't send all
kinds of @tech{S-expression}s. The data definitions for messages must
therefore select a subset of suitable @tech{S-expression}s. As for the
@|S-expression|s, but usually @tech{world} programs don't send all
kinds of @|S-expression|s. The data definitions for messages must
therefore select a subset of suitable @|S-expression|s. As for the
state of the server and the worlds, they must reflect how they currently
relate to the universe. Later, when we design their ``local'' behavior, we
may add more components to their state space.
@ -1745,7 +1748,7 @@ The final step is to design the ball @tech{world}. Recall that each world
))
The definition says that initially a @tech{world} is passive.
The communication protocol and the refined data definition of @tech{WorldState}
The communication protocol and the refined data definition of @|WorldState|
imply a number of contract and purpose statements:
@(begin
@ -1769,7 +1772,7 @@ The communication protocol and the refined data definition of @tech{WorldState}
Let's design one function at a time, starting with @emph{receive}. Since
the protocol doesn't spell out what @emph{receive} is to compute, let's
create a good set of functional examples, exploiting the structure of the
data organization of @tech{WorldState}:
data organization of @|WorldState|:
@(begin
#reader scribble/comment-reader