help/info/altstep.html

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   8  Contributors:
   9   Baji, Laszlo
  10   Balasko, Jeno
  11   Farkas, Laszlo
  12   Szabados, Kristof
  13   Szabo, Janos Zoltan – initial implementation
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  19 <title>altstep</title>
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  38 <h1>altstep</h1>
  39 <hr align="left" width="75%">
  40 <p>The keyword is used to specify default behavior or to structure the alternatives of an <b><font face="Courier New" color="#003258" size="4">alt</font></b> statement. Altsteps are similar to
  41 functions but the altstep body defines a set of alternatives (cf. <a href="alt.html"><b><font face="Courier New" color="#003258" size="4">alt</font></b></a>).&nbsp;
  42 <ul>
  43   <li>An altstep that is activated as default shall only have <b><font face="Courier New" color="#003258" size="4">in</font></b> parameters, port parameters and timer parameters.</li>
  44   <li>An altstep that is only invoked as an alternative in an alt statement or as stand-alone statement may have <b><font face="Courier New" color="#003258" size="4">in</font></b>, <b><font
  45     face="Courier New" color="#003258" size="4">out</font></b>and <b><font face="Courier New" color="#003258" size="4">inout</font></b> parameters.</li>
  46   <li>Altsteps may define local definitions of constants, variables and timers but this is strongly deprecated.</li>
  47 </ul>
  48 <p>Related keywords:</p>
  49 <ul>
  50   <li><a href="alt.html"><b><font face="Courier New" color="#003258" size="4">alt</font></b></a></li>
  51   <li><a href="default.html"><b><font face="Courier New" color="#003258" size="4">default</font></b></a></li>
  52 </ul>
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  56   <tr>
  57     <td width="100%">
  58     <h3 align="left"><font face="Courier New" color="#003258" size="5"><b>altstep&nbsp;</b></font><i> altstep_identifier </i> <font face="Courier New" color="#003258" size="5"><b>(</b></font> [<i>
  59     altstep_parameter</i> ... ] <font face="Courier New" color="#003258" size="5"><b>)</b></font>[ <font face="Courier New" color="#003258" size="5"><b>runs on</b></font><i> component_reference </i>] <font
  60       face="Courier New" color="#003258" size="5"><b>{<br>
  61     &nbsp;&nbsp;&nbsp;&nbsp;</b></font> [ <i>local_definitions</i> ]&nbsp; <font face="Courier New" color="#003258" size="5"><b><br>
  62     &nbsp;&nbsp;&nbsp; [</b></font> [<i>guard_expression</i>] <font face="Courier New" color="#003258" size="5"><b>]</b></font> [<i>condition</i>] <font face="Courier New" color="#003258" size="5"><b>{</b></font>
  63     [<i>statement_block</i>] <font face="Courier New" color="#003258" size="5"><b>}<br>
  64     &nbsp;&nbsp;&nbsp; </b></font> ...<font face="Courier New" color="#003258" size="5"><b><br>
  65     };</b></font> &nbsp;</h3>
  66     </td>
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  69 </div>
  70 <ul>
  71   <li>
  72   <p>The <font face="Courier New" color="#003258" size="4"><b>altstep</b></font> keyword introduces the altstep definition.</p>
  73   </li>
  74   <li>
  75   <p><i>altstep_identifier</i> is the&nbsp;name used to refer to the altstep. Must begin with a letter, may contain letters, numbers and underscore characters. According to the&nbsp; <a
  76     href="../docs/naming.pdf" target="_blank">Naming convention</a>, the prefix <b> as_</b> is recommended.</p>
  77   </li>
  78   <li>
  79   <p><i>altstep_parameter</i> defines a formal parameter. The expression begins with an optional keyword indicating the parameter passing method (<a href="in.html"><font face="Courier New"
  80     size="4"><b>in</b></font></a>, <a href="out.html"><font face="Courier New" size="4"><b>out</b></font></a> or <a href="inout.html"><font face="Courier New" size="4"><b>inout</b></font></a>), continues
  81   with a reference to a built-in type (cf. <a href="const.html#par1">their list</a>) or a <a href="type.html"> referenced type</a> and ends by a parameter identifier. <b>...</b>
  82   indicates that&nbsp; several parameters may be specified; they are separated by commas.</p>
  83   </li>
  84   <li>
  85   <p>The optional keywords <font face="Courier New" color="#003258" size="4"><b>runs on</b></font> makes component constants, variables, timers and ports visible inside the altstep</p>
  86   </li>
  87   <li>
  88   <p><i>component_reference</i> refers to the component. It is composed of two parts: the module identifier (may be omitted) and the component tpye identifier. The two parts are linked by a dot.</p>
  89   </li>
  90   <li>
  91   <p>The optional <i>local_definitions</i> may include constants, variables and timers visible inside the altstep. It is not recommended to use them.</p>
  92   </li>
  93   <li>
  94   <p>Each alternative begins with an optional <i>guard_expression</i> with the following options:</p>
  95   <ul>
  96     <li>empty guard (note that the brackets must be written) The <i>statement_block</i> will be executed if <i>condition</i> is met.&nbsp;</li>
  97     <li>Boolean expression. The <i>statement_block</i> will be executed if the Boolean expression evaluates to true AND <i>condition</i> is met.</li>
  98     <li>
  99     <p><font face="Courier New" color="#003258" size="4"><b>else</b></font> keyword. The <i>statement_block</i> will always be executed.&nbsp; No <i>condition</i> may appear in the branch.</p>
 100     </li>
 101   </ul>
 102   </li>
 103   <li>
 104   <p><i>condition</i> may be a communication or a timer event or the termination of a parallel test component. The following operations may be written here: <a href="receive.html"><b><font
 105     face="Courier New" color="#003258" size="4">receive</font></b></a>, <a href="trigger.html"><b><font face="Courier New" color="#003258" size="4">trigger</font></b></a>, <a href="getcall.html"><b><font
 106     face="Courier New" color="#003258" size="4">getcall</font></b></a>, <a href="getreply.html"><b><font face="Courier New" color="#003258" size="4">getreply</font></b></a>, <a href="catch.html"><b><font
 107     face="Courier New" color="#003258" size="4">catch</font></b></a>, <a href="check.html"><b><font face="Courier New" color="#003258" size="4">check</font></b></a>, <a href="timeout.html"><b><font
 108     face="Courier New" color="#003258" size="4">timeout</font></b></a> and <a href="done.html"><b><font face="Courier New" color="#003258" size="4">done</font></b></a>.</p>
 109   </li>
 110   <li>
 111   <p>The optional <i>statement_block</i> contains one or more statements separated by semicolons. When empty, the curly brackets must be written.</p>
 112   </li>
 113   <li>
 114   <p><b>...</b> indicates that&nbsp; several branches may occur in the <font face="Courier New" color="#003258" size="4"><b>altstep</b></font> body. There is no separator between them.</p>
 115   </li>
 116 </ul>
 117 <hr align="left" width="50%">
 118 <p>Example:
 119 <p><font face="Courier New">altstep as_AltSet_A(in integer pl_MyPar1) runs on MyComponentType_ct {<br>
 120 &nbsp;&nbsp;&nbsp;[]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;L1_PCO.receive { setverdict(pass) }&nbsp;<br>
 121 &nbsp;&nbsp;&nbsp;[x&lt;=1] L2_PCO.receive { setverdict(inconc) }&nbsp;<br>
 122 &nbsp;&nbsp;&nbsp;[else]&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;{ setverdict(fail); stop }&nbsp;<br>
 123 };</font>
 124 <p>The altstep called as_AltSet_A is defined. It has a read/only parameter called pl_MyPar1. The definitions made in the component MyComponentType_ct are visible to the altstep. The first branch
 125 is activated if a message has been received on port L1_PCO. The verdict is set to pass. The second branch is activated if a message has been received on port L2_PCO and the variable x is not grater
 126 then one. In this case the verdict is set to inconclusive. The last branch is activated if none of the ports has received a messages. The verdict is set to fail and test execution is stopped.</p>
 127 <hr align="left" width="25%">
 128 <hr align="left" width="25%">
 129 <p><a HREF="BNF.html#altstepdef">BNF definition</a> of <font face="Courier New"> altstep</font></p>
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