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<head><title>GlobalAssignHook -- hook for assignment to global variables</title>
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<div><h1>GlobalAssignHook -- hook for assignment to global variables</h1>
<div class="single"><h2>Synopsis</h2>
<ul><li><div class="list"><dl class="element"><dt class="heading">Usage: </dt><dd class="value"><div><tt>X.GlobalAssignHook = f</tt></div>
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<li><div class="single">Inputs:<ul><li><span><tt>X</tt>, <span>a <a href="___Type.html">type</a></span></span></li>
<li><span><tt>f</tt>, <span>a <a href="___Function.html">function</a></span>, of two variables: the symbol to which a value is about to be assigned, and the value being assigned</span></li>
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<li><div class="single">Consequences:<ul><li><tt>f</tt> will be called just before an assignment to a global variable of an instance of class <tt>X</tt> occurs</li>
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<div class="single"><h2>Description</h2>
<div><p>This technique is used, for example, for instances of <a href="___Type.html" title="the class of all types">Type</a> and <a href="___Ring.html" title="the class of all rings">Ring</a> to arrange for the name of the type or ring to be set to the name of the global variable to which it is first assigned. The functions <a href="_global__Assign__Function.html" title="the standard method for the global assignment hook">globalAssignFunction</a> and <a href="_global__Release__Function.html" title="the standard method for the global variable release hook">globalReleaseFunction</a> may installed as methods for this purpose.</p>
<table class="examples"><tr><td><pre>i1 : RR.GlobalAssignHook = (sym,val) -> << "--about to assign " << val << " to " << sym << endl;</pre>
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<tr><td><pre>i2 : a = 4.5
--about to assign 4.5 to a
o2 = 4.5
o2 : RR (of precision 53)</pre>
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<div class="single"><h2>See also</h2>
<ul><li><span><a href="___Global__Release__Hook.html" title="">GlobalReleaseHook</a></span></li>
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<div class="waystouse"><h2>For the programmer</h2>
<p>The object <a href="___Global__Assign__Hook.html" title="hook for assignment to global variables">GlobalAssignHook</a> is <span>a <a href="___Symbol.html">symbol</a></span>.</p>
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