46 lines
1.3 KiB
Racket
46 lines
1.3 KiB
Racket
#lang scribble/doc
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@(require scribble/manual
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(for-label scheme
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teachpack/htdp/arrow-gui))
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@title[#:tag "arrow-gui"]{An Arrow GUI: arrow-gui.ss}
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@declare-exporting[teachpack/htdp/arrow-gui]
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The teachpack provides operations for creating and manipulating an arrow
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GUI. We recommend using the @seclink["world"]{world teachpack} instead.
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@deftech{modelT} @scheme[(-> button% event% true)]
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A @tech{modelT} is a function that accepts and ignores two arguments.
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@defproc[(control) symbol?]{Reads out the current state of the message
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field.}
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@defproc[(view [s (or/c string? symbol?)]) true]{Displays @scheme[s] in the
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message field.}
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@defproc[(connect [l (unsyntax @tech{modelT})][r (unsyntax @tech{modelT})][u (unsyntax @tech{modelT})][d (unsyntax @tech{modelT})]) true]{Connects four
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controllers with the four directions in the arrow window.}
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Example:
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@(begin
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#reader scribble/comment-reader
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(schemeblock
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;; Advanced
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(define (make-model dir)
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(lambda (b e)
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(begin
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(view dir)
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(printf "~a ~n" (control)))))
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(connect
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(make-model "left")
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(make-model "right")
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(make-model "up")
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(make-model "down"))
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))
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Now click on the four arrows. The message field contains the current
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direction, the print-out the prior contents of the message field.
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