chap3.txt

  
  3 Extending the OpenMath package
  
  
  3.1 Exploring the range of supported symbols
  
  The  OpenMath  package  supports  such  basic OpenMath objects as integers (
  <OMI>  ),  character  strings ( <OMSTR> ) and variables ( <OMVAR> ). Besides
  that,  it  supports  a number of OpenMath content dictionaries (some of them
  only partially, dependently on their relevance to GAP). To see which symbols
  from  which  content  dictionaries  are  supported  for  the conversion from
  OpenMath  to GAP, explore the global record OMsymRecord. Its components have
  names  of appropriate CDs, and subcomponents of each component have names of
  symbols  from  the  corresponding  CD.  If the value of the component is not
  equal to fail, then it contains the function or the object which is used for
  conversion. The following example of the entry for the nums1 CD demonstrates
  a combination of all possible cases:
  
    Example  
    
    gap> Display( OMsymRecord.nums1 );          
    rec(
      NaN := nan,
      based_integer := fail,
      e := 2.718281828459045,
      gamma := fail,
      i := E(4),
      infinity := infinity,
      pi := 3.141592653589793,
      rational := function ( x )
            return OMgapId( [ OMgap2ARGS( x ), x[1] / x[2] ] )[2];
        end )
    
  
  
  OMsymRecord  contains  all symbols for which conversion from OpenMath to GAP
  is  supported  except  some  special symbols related with errors and special
  procedures from the SCSCP package which are treated separately.
  
  To check quickly if GAP can parse a given OpenMath object, copy the OpenMath
  code and paste it directly into standard input after the following command:
  
    Example  
    
    gap> s:= InputTextUser();; g := OMGetObject(s); CloseStream(s);
    
  
  
  The  main  tool  for the conversion from GAP to OpenMath is OMPut( <writer>,
  <object>  ).  A  number  of  methods  for  OMPut  are  installed in the file
  openmath/gap/omput.gi.
  
  To  check  quickly  whether  the  object  may be converted to OpenMath, call
  OMprint for that object, for example:
  
    Example  
    
    gap> OMPrint( [ [1..10], ZmodnZObj(2,6), (1,2) ] );                
    <OMOBJ xmlns="http://www.openmath.org/OpenMath" version="2.0">
    	<OMA>
    		<OMS cd="list1" name="list"/>
    		<OMA>
    			<OMS cd="interval1" name="integer_interval"/>
    			<OMI>1</OMI>
    			<OMI>10</OMI>
    		</OMA>
    		<OMA>
    			<OMS cd="integer2" name="class"/>
    			<OMI>2</OMI>
    			<OMI>6</OMI>
    		</OMA>
    		<OMA>
    			<OMS cd="permut1" name="permutation"/>
    			<OMI>2</OMI>
    			<OMI>1</OMI>
    		</OMA>
    	</OMA>
    </OMOBJ>
    
  
  
  The  package  is  in  the  continuous development and will support even more
  symbols  in  the  future. In the meantime, if you will have any requests for
  the support for particular symbols, please contact Alexander Konovalov.
  
  
  3.2 Adding support for private content dictionaries and symbols
  
  There  is  also  a way for the user to extend the package adding support for
  private and experimental CDs or separate symbols. We allocated the directory
  openmath/private  for  this  purposes,  and  currently  it  contain the file
  private.g  for  conversions from OpenMath to GAP and the file private.gi for
  conversions from GAP to OpenMath for some symbols from private CDs contained
  in the openmath/cds directory.
  
  In  particular,  we extended the package with the following private OpenMath
  symbols:
  
      group1.group_by_generators  which allows us to input and output groups
        given by their generators as this is a natural way to create groups in
        GAP;
  
      semigroup1.semigroup_by_generators   and  monoid1.monoid_by_generators
        following the same considerations for semigroups and monoids;
  
      pcgroup1.pcgroup_by_pcgscode for PcGroups given by their pcgs code and
        order;
  
      record1.record for records as they are important data structures which
        we  want  to  pass  in  a straightforward manner between different GAP
        instances;
  
      transform1.transformation  to  support transformations, transformation
        semigroups and their automorphism groups.
  
  The  file private.g is loaded from openmath/gap/new.g, and the private.gi is
  loaded  from  openmath/gap/read.g.  If  the user would like to add own code,
  this may be done either by adding it to these files or by placing additional
  files in openmath/private directory and load them similarly to private.g and
  private.gi.  We will welcome user's contributions in the form of the code to
  support  existing content dictionaries from the OpenMath web site or private
  content dictionaries, if they may be interesting for a wider community.