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changed world.ss interface (docs) to accommodate stepper

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svn: r1579
This commit is contained in:
Matthias Felleisen 2005-12-10 15:19:39 +00:00
parent 6b33960bb4
commit ea35acdfc7
1 changed files with 27 additions and 21 deletions
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46
teachpack/htdp/Docs/world.thtml
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@ -12,19 +12,35 @@ students to simulate a small world of animated drawings and games:
and makes w the first world and makes w the first world
<li><code>on-tick-event : (World -> World) -> true</code><br> <li><code>on-tick-event : (World -> World) -> true</code><br>
<code>(on-tick-event tock)</code> <code>(on-tick-event tock)</code> means that DrScheme must call <code>tock</code>
calls tock on the current world for every clock tick; on the current world every time the clock ticks; it uses the result as the next world
the result is the next world
<li><code>on-key-event : (KeyEvent World -> World) -> true</code><br> <li><code>on-key-event : (KeyEvent World -> World) -> true</code><br>
<code>(on-key-event react)</code> <code>(on-key-event change)</code> means that DrScheme must call
calls react on every keystroke event, <code>change</code> on the current world for every keystroke event; it uses
with a char or a symbol representing the keystroke, the result as the next world
and the current world; the result is the next world
<pre>
<code>
;; A KeyEvent is one of:
;; -- Char (char?)
;; -- Symbol (symbol?)
</code>
When the Keyevent is a char, the programmer (user of the computer) has hit an
alphanumeric key. Symbols such as <code>'left</code>, <code>'right</code>,
<code>'up</code>, <code>'down</code>, <code>'release</code> denote arrow keys
or the events of releasing a key on the keypad.
</pre>
<li><code>on-redraw : (World -> Image) -> true</code><br>
<code>(on-tick-event world->image)</code> means that DrScheme
calls <code>world->image</code> whenever the canvas must be redrawn; the
result is displayed in the teachpack's canvas
<li><code>end-of-time : -> World</code><br> <li><code>end-of-time : -> World</code><br>
<code>(end-of-time)</code> When DrScheme evaluates <code>(end-of-time)</code>, it stops the clock; no
stops the clock. further tick events, key events, or redraw events take place until the world
is created again.
</menu></p> </menu></p>
<p>The rest are functions for creating scenes: <p>The rest are functions for creating scenes:
@ -47,17 +63,7 @@ students to simulate a small world of animated drawings and games:
shows the list of images in loi, time-delayed shows the list of images in loi, time-delayed
</menu></p> </menu></p>
<p>Finally, the teachpack also adds some one new form of syntax to the <p>Finally, the teachpack provides all the functions that image.ss provides. </p>
language:
<menu>
<li><code>
(<b>update</b> &lt;expression&gt; <b>produce</b> &lt;expression&gt;)</code><br>
update the canvas of the world with the first expression; the result
is the value of the second expression.
</menu>
Both update and produce are new keywords. </p>
<p>The teachpack provides all the functions that image.ss provides. </p>
{(include "foot.tinc")} {(include "foot.tinc")}