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<div><a href="index.html" title="">Macaulay2Doc</a> > <a href="___The_sp__Macaulay2_splanguage.html" title="">The Macaulay2 language</a> > <a href="_variables.html" title="The variables of a complex or co-complex.">variables</a> > <a href="_assigning_spvalues.html" title="">assigning values</a></div>
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<div><h1>assigning values</h1>
<div>Use an equal sign to assign values to variables.<table class="examples"><tr><td><pre>i1 : x = "abcde"
o1 = abcde</pre>
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<tr><td><pre>i2 : x
o2 = abcde</pre>
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Before assignment, any reference to a variable provides the symbol with that name. After assignment, the assigned value is provided. The variable created is global, in the sense that any code placed elsewhere that contains a reference to a variable called <tt>x</tt> will refer to the one we just set.<p/>
It is important to distinguish between a symbol and its value. The initial value of a global symbol is the symbol itself, and the initial value of a local variable is <a href="_null.html" title="the unique member of the empty class">null</a>. One possibility for confusion comes from the possibility of having a symbol whose value is another symbol; it's even more confusing if the two symbols have the same name but different scopes, for example, if one of them is global and the other is local.<table class="examples"><tr><td><pre>i3 : y
o3 = y
o3 : Symbol</pre>
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<tr><td><pre>i4 : y = z
o4 = z
o4 : Symbol</pre>
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<tr><td><pre>i5 : y
o5 = z
o5 : Symbol</pre>
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<tr><td><pre>i6 : z = 444
o6 = 444</pre>
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<tr><td><pre>i7 : z
o7 = 444</pre>
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<tr><td><pre>i8 : y
o8 = z
o8 : Symbol</pre>
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In the example above, the final value of <tt>y</tt> is the symbol <tt>z</tt>, even though the symbol z has acquired a value of its own. The function <tt>value</tt> can be used to get the value of a symbol.<table class="examples"><tr><td><pre>i9 : value y
o9 = 444</pre>
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The operator <a href="__lt-.html" title="assignment with left side evaluated"><-</a> can be used to set the value of a symbol. This operator differs from <a href="__eq.html" title="assignment">=</a> in that the symbol or expression on the left hand side is evaluated.<table class="examples"><tr><td><pre>i10 : y <- 555
o10 = 555</pre>
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<tr><td><pre>i11 : y
o11 = z
o11 : Symbol</pre>
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<tr><td><pre>i12 : z
o12 = 555</pre>
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<tr><td><pre>i13 : y = 666
o13 = 666</pre>
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<tr><td><pre>i14 : y
o14 = 666</pre>
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<tr><td><pre>i15 : z
o15 = 555</pre>
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One reason the user needs to understand this concept is that assignments with the operator <a href="__lt-.html" title="assignment with left side evaluated"><-</a> are occasionally done on the user's behalf by bits of code already in the system, for example, when creating a polynomial ring the prospective variables are given new values that are the generators of the polynomial ring.<p/>
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<div class="single"><h2>See also</h2>
<ul><li><span><a href="___Global__Assign__Hook.html" title="hook for assignment to global variables">GlobalAssignHook</a> -- hook for assignment to global variables</span></li>
<li><span><a href="___Global__Release__Hook.html" title="">GlobalReleaseHook</a></span></li>
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