| <html><head><META http-equiv="Content-Type" content="text/html; charset=ISO-8859-1"><title>5.8.2. Directed Formal Parameters</title><link href="style.css" rel="stylesheet" type="text/css"><meta content="DocBook XSL Stylesheets V1.72.0" name="generator"><link rel="start" href="index.html" title="The VIATRA2 Model Transformation Framework"><link rel="up" href="sec_Parameters.html" title="5.8. Parameters and Variable Lists"><link rel="prev" href="def_FormalParameter.html" title="5.8.1. Formal Parameters"><link rel="next" href="def_ActualParameter.html" title="5.8.3. Actual Parameters"></head><body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"><div class="navheader"><table summary="Navigation header" width="100%"><tr><th align="center" colspan="3">5.8.2. Directed Formal Parameters</th></tr><tr><td align="left" width="20%"><a accesskey="p" href="def_FormalParameter.html">Prev</a> </td><th align="center" width="60%">5.8. Parameters and Variable Lists</th><td align="right" width="20%"> <a accesskey="n" href="def_ActualParameter.html">Next</a></td></tr></table><hr></div><div class="sect3" lang="en"><div class="titlepage"><div><div><h4 class="title"><a name="def_DirectedFormalParameter"></a>5.8.2. Directed Formal Parameters</h4></div></div></div><div class="tip" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Tip: Description"><tr><td valign="top" align="center" rowspan="2" width="25"><img alt="[Tip]" src="images/tip.png"></td><th align="left"><a name="def_DirectedFormalParameter_Description"></a>Description</th></tr><tr><td valign="top" align="left"><p> | |
| <span class="strong"><strong>Directed formal parameters</strong></span> | |
| <a name="N12FC7" class="indexterm"></a> | |
| <a name="N12FCC" class="indexterm"></a> | |
| define the interface of a <a href="def_GTRuleDef.html" title="3.1.1. Graph Transformation Rule Definition">GT rule</a> or an | |
| <a href="def_AsmRuleDef.html" title="4.1.1. ASM Rule Definition">ASM rule</a> by a list of | |
| <a href="def_Variable.html" title="5.7.2. Variable">ASM variables</a>. | |
| </p></td></tr></table></div><div class="important" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Important: Syntax"><tr><td valign="top" align="center" rowspan="2" width="25"><img alt="[Important]" src="images/important.png"></td><th align="left"><a name="def_DirectedFormalParameter_Syntax"></a>Syntax</th></tr><tr><td valign="top" align="left"><pre class="programlisting"> | |
| DirectedFormalParamsAST ::= DirectionKindAST <a href="def_Variable.html" title="5.7.2. Variable">VariableDefAST</a> | |
| | DirectedFormalParamsAST <span class="token">,</span> DirectionKindAST <a href="def_Variable.html" title="5.7.2. Variable">VariableDefAST</a> | |
| DirectionKindAST ::= <span class="token">in</span> | <span class="token">out</span> | <span class="token">inout</span> | |
| </pre><p> | |
| <span class="strong"><strong>Directed formal parameters</strong></span> are defined by | |
| is a comma-separated list of variables (each having a direction specification). | |
| It can contain an arbitrary number of variables (including none). | |
| In contrast to the <a href="def_FormalParameter.html" title="5.8.1. Formal Parameters">formal parameters</a>, | |
| it defines a direction for each parameter, namely either <code class="computeroutput">in</code>, | |
| <code class="computeroutput">out</code> or <code class="computeroutput">inout</code>. | |
| </p></td></tr></table></div><div class="note" style="margin-left: 0.5in; margin-right: 0.5in;"><table border="0" summary="Note: Semantics"><tr><td valign="top" align="center" rowspan="2" width="25"><img alt="[Note]" src="images/note.png"></td><th align="left"><a name="def_DirectedFormalParameter_Semantics"></a>Semantics</th></tr><tr><td valign="top" align="left"><p> | |
| An <span class="emphasis"><em>input-only variable</em></span> (with tag <code class="computeroutput">in</code>) takes the value of the | |
| actual parameter, but at the end of the execution of the rule the value of | |
| the actual parameter is not updated. | |
| </p><p> | |
| An <span class="emphasis"><em>output-only variable</em></span>(with tag <code class="computeroutput">out</code>) does not take the value of | |
| the actual parameter: it is considered as undefined having the | |
| <a href="def_UndefinedValue.html" title="5.4.2. Undefined Value">undefined value</a> (<code class="computeroutput">undef</code>). | |
| At the end of the execution of the rule, the value of the actual parameter is overwritten with the value | |
| of the variable defined as formal parameter. | |
| </p><p> | |
| An <span class="emphasis"><em>input-output variable</em></span>(with tag <code class="computeroutput">inout</code>) takes the value of the | |
| actual parameter, and at the end of the execution of the rule the value of | |
| the actual parameter is updated with the value of the variable defined as | |
| formal parameter. | |
| </p></td></tr></table></div><div class="highlights"><a name="def_DirectedFormalParameter_UsedBy"></a><p><b>Used By: </b> | |
| <a href="def_GTRuleDef.html" title="3.1.1. Graph Transformation Rule Definition">GT rule definition</a>, | |
| <a href="def_AsmRuleDef.html" title="4.1.1. ASM Rule Definition">ASM rule definition</a> | |
| </p></div><div class="highlights"><a name="def_DirectedFormalParameter_SeeAlso"></a><p><b>See Also: </b> | |
| <a href="def_FormalParameter.html" title="5.8.1. Formal Parameters">formal parameters</a>, | |
| <a href="def_ActualParameter.html" title="5.8.3. Actual Parameters">actual parameter</a>, | |
| <a href="def_UndefinedValue.html" title="5.4.2. Undefined Value">undefined value</a> | |
| </p></div></div><div class="navfooter"><hr><table summary="Navigation footer" width="100%"><tr><td align="left" width="40%"><a accesskey="p" href="def_FormalParameter.html">Prev</a> </td><td align="center" width="20%"><a accesskey="u" href="sec_Parameters.html">Up</a></td><td align="right" width="40%"> <a accesskey="n" href="def_ActualParameter.html">Next</a></td></tr><tr><td valign="top" align="left" width="40%">5.8.1. Formal Parameters </td><td align="center" width="20%"><a accesskey="h" href="index.html">Home</a></td><td valign="top" align="right" width="40%"> 5.8.3. Actual Parameters</td></tr></table></div></body></html> |