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* Chickadee: (chickadee).     Game programming toolkit for Guile.

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<span id="Live-Coding"></span><div class="header">
<p>
Previous: <a href="Window-Manipulation.html#Window-Manipulation" accesskey="p" rel="prev">Window Manipulation</a>, Up: <a href="Kernel.html#Kernel" accesskey="u" rel="up">Kernel</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Index.html#Index" title="Index" rel="index">Index</a>]</p>
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<hr>
<span id="Live-Coding-1"></span><h4 class="subsection">2.1.4 Live Coding</h4>

<p>One of the biggest appeals of any Lisp dialect is the ability to use
the &ldquo;read-eval-print loop&rdquo; (REPL for short) to build programs
iteratively and interactively while the program is running.  However,
programs that run in an event loop and respond to user input (such as
a video game) require special care for this workflow to be pleasant.
Chickadee provides no built-in support for live coding, but it&rsquo;s
fairly easy to hook up a special kind of REPL yourself.
</p>
<p>First, create a cooperative REPL server (It&rsquo;s important to use Guile&rsquo;s
cooperative REPL server instead of the standard REPL server in
<code>(system repl server)</code> to avoid thread synchronization issues).
Then, in the game loop&rsquo;s update procedure, call
<code>poll-coop-repl-server</code> and pass the REPL object.  Here is a
template to follow:
</p>
<div class="example">
<pre class="example">(use-modules (chickadee)
             (system repl coop-server))

(define repl (spawn-coop-repl-server))

(define (update dt)
  (poll-coop-repl-server repl)
  ...)

(run-game #:update update ...)
</pre></div>

<p>To use the REPL, connect to it via port 37146.  Telnet will do the
trick, but using the <a href="https://www.nongnu.org/geiser/">Geiser</a>
extension for Emacs is by far the best way to develop at the REPL with
Guile.  Use <code>M-x connect-to-guile</code> to connect to the REPL server.
</p>



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