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  - Authors:
  -   Christian Schulte <schulte@ps.uni-sb.de>
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  - Copyright:
  -   Christian Schulte, 1998
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  -   $Date: 2002/08/20 09:40:50 $ by $Author: kornstae $
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<Chapter id="chapter.system">
  <Title/Miscelleanous System Support: <<System>>/

  <p>
    The <<System>> module contains procedures providing functionality
    related to the Mozart Engine. 

  <section id="section.system.control">
    <title/System Control/

    <p>
    <list>
      <entry><<gcDo>>
        <index class=tails/<<System>><And><<gcDo>>/
      <synopsis>
        <<{System.gcDo}>>
      <item>
        Invokes garbage collection.
    </list>
 
  <section id="section.system.printing">
    <title/Printing/

    <p>
      The procedures to print values and virtual strings choose the
      output device for the printed text as follows:
      <list enum>
        <item> If Mozart is running standalone, the standard output or 
          standard error device is chosen (depending on the procedure).
        <item> Otherwise the Oz Programming Interface is chosen as output
          device.
      </list>
     
    <p>
     The procedures explained here differ from those provided by
     <<Open>> and <<OS>> in that they can be used to print information
     in subordinated computation spaces to support debugging.

    <p>
    <list>
      <entry><<print>>
        <index class=tails/<<System>><And><<print>>/
      <synopsis>
        <<{System.print ?_{X}}>>
      <item>
        The current information on ?_{X} is printed without a
        following newline.
      <p>
        The output is limited in depth and width by system parameters
        that can be configured either by the Oz Panel (see <ptr.extern
        to="ozdoc:panel">) or by <<Property.put>>
        (see <ptr to="chapter.property">).

      <p>
        A width of <math/n/ means that for lists at most <math/n/
        elements and for records at most <math/n/ fields are printed,
        the unprinted elements and fields are abbreviated by
        <kbd/,,,/. A depth of <math/n/ means that trees are printed to
        a depth limit of <math/n/ only, deeper subtrees are
        abbreviated by <kbd/,,,/. 

      <p>
        The printed text appears on standard output.

      <entry id=system.show><<show>>
        <index class=tails/<<System>><And><<show>>/
      <synopsis>
        <<{System.show ?_{X}}>>
      <item>
        The current information on ?_{X} is printed with a
        following newline.
      <p>
        The output is limited in depth and width as with
        <<System.print>>. 
      <p>
        The printed text appears on standard output.


      <entry><<printError>>
        <index class=tails/<<System>><And><<printError>>/
      <synopsis>
        <<{System.printError ?_{V}}>>
      <item> 
        Prints the virtual string ?_{V} without a newline.
      <p>
        The printed text appears on standard error.

      <entry><<showError>>
        <index class=tails/<<System>><And><<showError>>/
      <synopsis>
        <<{System.showError ?_{V}}>>
      <item> 
        Prints the virtual string ?_{V} followed by a newline.
      <p>
        The printed text appears on standard error.


      <entry><<printInfo>>
        <index class=tails/<<System>><And><<printInfo>>/
      <synopsis>
        <<{System.printInfo ?_{V}}>>
      <item> 
        Prints the virtual string ?_{V} without a newline.
      <p>
        The printed text appears on standard output.

      <entry><<showInfo>>
        <index class=tails/<<System>><And><<showInfo>>/
      <synopsis>
        <<{System.showInfo ?_{V}}>>
      <item> 
        Prints the virtual string ?_{V} followed by a newline.
      <p>
        The printed text appears on standard output.

    </list>

  <section id="section.system.misc">
    <title/Miscellaneous/

    <p>
    <list>
      <entry><<eq>>
        <index class=tails/<<System>><And><<eq>>/
      <synopsis>
        <<{System.eq ?_{X} ?_{Y} ??{B}}>>
      <item> 
        Tests whether ?_{X} and ?_{Y} refer to the same value node in
        the store. 

      <entry><<nbSusps>>
        <index class=tails/<<System>><And><<nbSusps>>/
      <synopsis>
        <<{System.nbSusps ?_{X} ??{I}}>>
      <item> 
        Returns the number of suspensions on ?_{X}, that is the number
        of threads and propagators that suspend on ?_{X}. 

      <entry><<onToplevel>>
	<index class=tails/<<System>><And><<onToplevel>>/
      <synopsis>
	<<{System.onToplevel ??{B}}>>
      <item>
	Returns <<true>> iff the current thread is executing in the
	top level space and not within a deep space.

    </list>

  </Chapter>


