help/info/activate.html

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  13 <title>activate</title>
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  32 <h1>activate</h1>
  33 <hr align="left" width="75%">
  34 <p>The operation is used to activate a default context (i.e., an <a href="altstep.html"><b><font face="Courier New" size="4">altstep</font></b></a>). It returns a reference to the activated
  35 default.</p>
  36 <ul>
  37   <li>Default context is a set of branches (cf. <a href="altstep.html"><b><font face="Courier New" size="4">altstep</font></b></a>) that is implicitly appended at the end of all <a
  38     href="alt.html"><b><font size="4" face="Courier New">alt</font></b></a> statements (except if the alt has an else branch) and after all stand-alone receive/timeout/done … statements. When no
  39   branch of the alt matches the received message, the previously activated default(s) are examined.</li>
  40   <li>The default reference can be used to <b><a href="deactivate.html"><font face="Courier New" size="4">deactivate</font></a></b> a given default.</li>
  41   <li>The special value <b><a href="null.html"><font face="Courier New" size="4">null</font></a></b> is available to indicate an undefined default reference, e.g. for the initialization of
  42   variables to handle default references.</li>
  43   <li>It is possible to have several defaults activated at same time and deactivate them one by one. The last activated default will be placed first in the list of the activated defaults.</li>
  44 </ul>
  45 <p>Related keywords:</p>
  46 <ul>
  47   <li><a href="alt.html"><b><font face="Courier New" color="#003258" size="4">alt</font></b></a></li>
  48   <li><a href="altstep.html"><b><font face="Courier New" color="#003258" size="4">alstep</font></b></a></li>
  49   <li><a href="deactivate.html"><b><font face="Courier New" color="#003258" size="4">deactivate</font></b></a></li>
  50   <li><a href="default.html"><b><font face="Courier New" color="#003258" size="4">default</font></b></a></li>
  51   <li><a href="null.html"><b><font face="Courier New" color="#003258" size="4">null</font></b></a></li>
  52 </ul>
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  58     <td width="100%">
  59     <h3 align="center"><font face="Courier New" color="#003258" size="5"><b>activate(</b></font><i>altstep_ref</i><font face="Courier New" color="#003258" size="5"><b>)</b></font></h3>
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  63 </center>
  64 </div>
  65 <ul>
  66   <li>
  67   <p><i>altstep_ref</i> is the&nbsp; reference to the altstep to be activated as default.
  68   </li>
  69 </ul>
  70 <hr align="left" width="50%">
  71 <p>Example 1:
  72 <p><font face="Courier New">var default vd_DefaultVar := null;<br>
  73 DefaultVar := activate(as_MyDefAltstep());<br>
  74 </font>
  75 <p>The variable DefaultVar will hold the reference to the altstep activated as default (as_MyDelAltstep).</p>
  76 <hr align="left" width="25%">
  77 <hr align="left" width="25%">
  78 <p><a HREF="BNF.html#activateop">BNF definition</a> of <font face="Courier New">activate</font></p>
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