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<h4 class="subsection" id="Accessing-Global-Variables-in-Oct_002dFiles-1"><span>A.1.7 Accessing Global Variables in Oct-Files<a class="copiable-link" href="#Accessing-Global-Variables-in-Oct_002dFiles-1"> ¶</a></span></h4>
<p>Global variables allow variables in the global scope to be accessed. Global
variables can be accessed within oct-files by using the support functions
<code class="code">global_varval</code><!-- /@w --> and <code class="code">global_assign</code><!-- /@w --> from the current
interpreter’s symbol table. Both functions take as first argument a string
representing the variable name to be obtained or assigned. The second
argument of <code class="code">global_assign</code><!-- /@w --> is the value to be assigned. An
example of the use of these two functions is
</p>
<div class="example">
<pre class="verbatim">#include <octave/oct.h>
#include <octave/interpreter.h>
DEFMETHOD_DLD (globaldemo, interp, args, , "Global Demo")
{
if (args.length () != 1)
print_usage ();
octave_value retval;
std::string s = args(0).string_value ();
octave::symbol_table& symtab = interp.get_symbol_table ();
octave_value tmp = symtab.global_varval (s);
if (tmp.is_defined ())
retval = tmp;
else
retval = "Global variable not found";
symtab.global_assign ("a", 42.0);
return retval;
}
</pre></div>
<p>An example of its use is
</p>
<div class="example">
<div class="group"><pre class="example-preformatted">global a b
b = 10;
globaldemo ("b")
⇒ 10
globaldemo ("c")
⇒ "Global variable not found"
num2str (a)
⇒ 42
</pre></div></div>
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