diff --git a/collects/teachpack/2htdp/scribblings/universe.scrbl b/collects/teachpack/2htdp/scribblings/universe.scrbl index 25b41981d7..e8da05e248 100644 --- a/collects/teachpack/2htdp/scribblings/universe.scrbl +++ b/collects/teachpack/2htdp/scribblings/universe.scrbl @@ -940,7 +940,7 @@ for universe programs. For example: } @item{Each event handler produces a @emph{bundle}, which is a structure - that contains the list of @emph{iworld}s to keep track of; the + that contains the list of @emph{iworld}s that the universe must track; the @tech{server}'s remaining state; and a list of mails to other worlds: @@ -948,8 +948,11 @@ for universe programs. For example: determines whether @scheme[x] is a @emph{bundle}.} @defproc[(make-bundle [low (listof iworld?)] [state any/c] [mails (listof mail?)]) bundle?]{ - creates a @emph{bundle} from a list of iworlds, a piece of data that represents a server - state, and a list of mails.} + creates a @emph{bundle} from a list of iworlds, a piece of data that + represents a server state, and a list of mails.} + +If an event handler returns a bundle with an empty list of worlds, the +universe server is restarted in the initial state. A @emph{mail} represents a message from an event handler to a world. The teachpack provides only a predicate and a constructor for these structures: @@ -960,7 +963,6 @@ teachpack provides only a predicate and a constructor for these structures: @defproc[(make-mail [to iworld?] [content sexp?]) mail?]{ creates a @emph{mail} from a @emph{iworld} and an @tech{S-expression}.} } - ] @; ----------------------------------------------------------------------------- @@ -1039,7 +1041,6 @@ The mandatory clauses of a @scheme[universe] server description are @scheme[w] is guaranteed to be on the list @scheme[low]. } }] - All proper event handlers produce a @emph{bundle}. The list of worlds in this @emph{bundle} becomes the server's list of worlds, meaning that only the server listens only to messages from "approved" worlds. The state in