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Parameters are very useful. See:<br>
<a class="moz-txt-link-freetext" href="http://docs.racket-lang.org/reference/parameters.html">http://docs.racket-lang.org/reference/parameters.html</a><br>
<br>
<br>
Neil Van Dyke wrote at 10/31/2011 01:06 PM:
<blockquote cite="mid:4EAED588.3010800@neilvandyke.org" type="cite">
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<a moz-do-not-send="true" class="moz-txt-link-abbreviated"
href="mailto:jkaczorek@aol.pl">jkaczorek@aol.pl</a> wrote at
10/31/2011 12:58 PM:<br>
<blockquote
cite="mid:8CE660583067BA6-E18-78A4E@Webmail-d112.sysops.aol.com"
type="cite"><font color="black" face="arial" size="2"><font
color="black" face="arial" size="2"><font face="Arial,
Helvetica, sans-serif"> Of course, I realize, that
redefinition of the variables is not good (functional)
programming style but sometimes it’s necessary. Is there a
possibility of such modifications without changing
language?</font></font></font></blockquote>
<br>
You might wish to use a parameter, like in the example below.<br>
<br>
<br>
#lang racket<br>
<br>
(define current-counter (make-parameter 0))<br>
<br>
(current-counter) ;==> 0<br>
<br>
(current-counter 42)<br>
<br>
(current-counter) ;==> 42<br>
<br>
(current-counter (+ 1 (current-counter)))<br>
<br>
(current-counter) ;==> 43<br>
<br>
<br>
In this example, I have named your variable to start with
"current-", just by convention to emphasize that a variable is a
parameter, but that's not actually necessary.<br>
<br>
</blockquote>
<br>
<div class="moz-signature">-- <br>
<a class="moz-txt-link-freetext" href="http://www.neilvandyke.org/">http://www.neilvandyke.org/</a><br>
<br>
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