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<html>
<head>
<title>Default Parameters.</title>
</head>
<body bgcolor="#dddddd">
<font color=brown>
<hr>
<center><h1>Default Parameters.</h1></center>
<hr>
<p>
Within C you could not provide default values for function
parameters. Well, C++ has come to your rescue.
<p>
<center>
<table border="1" width="80%" bgcolor="ivory">
<tr>
<td>
<pre>
#include <iostream.h>
void Func( int one, <b>int two=2, int three=3</b>);
main ()
{
Func(10, 20, 30);
Func<b>(10, 20); // Let the last parm default</b>
Func<b>(10); // Just provide the required parm.</b>
}
void Func( int one, int two, int three)
{
cout << "One = " << one << endl;
cout << "Two = " << two << endl;
cout << "Three = " << three << endl << endl;
}
</pre>
</td>
</tr>
</table>
</center>
<p>
From this example, you can see that the prototype/function declaration
gives default values for the second and third parameters. It is now
down to the programmer calling the function to decide how many
s/he wants to provide.
<p>
There are some basic rules that should be applied when using
default parameter values.
<ul>
<li>When a default is provided, all remaining parameters must be
given defaults. There can not be any holes.
<li>Default values must be of the correct type.
<li>Defaults can be placed on the function prototype or the function
definition. They can also be placed in both locations at the
same time. I have been told its good practice to place them
in the prototype only.
</ul>
<p>
<hr>
<h2>Examples:</h2>
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<hr>
<h2>See Also:</h2>
<img src="../../GRAPHICS/whiteball.gif" alt="o">
<a href="funcoverload.html">Function Name Overloading</a>.
</font>
<hr>
<font color=black>
<h2>C References</h2>
<p>
<img src="../../GRAPHICS/whiteball.gif" alt="o">
<a href="../../C/SYNTAX/functions.html">Function basics</a>.
</font>
<hr>
<p>
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<p>
<hr>
<font color=brown>
<address>Martin Leslie
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