Quelle output.xml Sprache: XML

   <Section><Heading>Calling Polymake and converting its output</Heading>

   <ManSection>
   <Meth Name="Polymake" Arg="poly option : PolymakeNolookup"/>
    <Description>

     This method calls the polymake program (see <Ref
     Var="POLYMAKE_COMMAND"/>) with the option
     <A>option</A>. You may use several keywords such as
     <C>"FACETS VERTICES"</C> as an option. The returned value is cut into blocks
     starting with keywords (which are taken from output and not
     looked up in <A>option</A>). Each block is then
     interpreted and translated into &GAP; readable form. This
     translation is done using the functions given in <Ref
     Var="ObjectConverters"/>.

     The first line of each block of polymake output is taken as a
     keyword and the according entry in <Ref Var="ObjectConverters"/>
     is called to convert the block into &GAP; readable form. If no
     conversion function is known, an info string is printed and <K>fail</K> is
     returned.

     If only one keyword has been given as <A>option</A>,
     <C>Polymake</C> returns the result of the conversion operation.
     If more than one keyword has been given or the output consists of
     more than one block, <C>Polymake</C> returns <K>fail</K>.

     In any case, the calculated values for each block are stored as
     known properties of the <K>PolymakeObject</K> <A>poly</A> as long
     as they are not <K>fail</K>.

     If <K>Polymake</K> is called with an option that corresponds to a
     name of a known property of <A>poly</A>, the known property is
     returned. In this case, there is no call of the external program.
     (see below for suppression of this feature).<P/>

     Note that the command <K>Polymake</K> returns <K>fail</K> if
     nothing is returned by the program polymake or more than one
     block of data is returned. For example, the returned value of
     <C>Polymake(poly,"VISUAL")</C> is always
     <K>fail</K>. Likewise, <C>Polymake(poly,"POINTS VERTICES")</C>
     will return <K>fail</K> (but may add new known properties to
     <A>poly</A>).

     For a description of the conversion functions, see chapter <Ref
     Chap="Converting"/>.<P/>

     If the option <A>PolymakeNolookup</A> is set to anything else
     than false, the polymake program is called even if <A>poly</A>
     already has a known property with name <A>option</A>.
  </Description>
  </ManSection>

  Note that whenever <Ref Meth="Polymake"/> returns <K>fail</K>, a description
  of the problem is stored in  <Ref Var="POLYMAKE_LAST_FAIL_REASON"/>.
  If you call <Ref Meth="Polymake"/> with more than one keyword,
  <Ref Var="POLYMAKE_LAST_FAIL_REASON"/> is changed before polymake is
  called. So any further reason to return <K>fail</K> will overwrite it.

  </Section>

   <Section><Heading>An Example</Heading>

   Let's generate a three dimensional permutahedron.

    <Example>
    <![CDATA[
    gap> S:=SymmetricGroup(3);
    Sym( [ 1 .. 3 ] )
    gap> v:=[1,2,3];
    [ 1, 2, 3 ]
    gap> points3:=Orbit(S,v,Permuted);;
         # project to reduce ambient dimension
    gap> points:=points3{[1..6]}{[1,2]};;
    gap> permutahedron:=CreatePolymakeObject();
    <polymake object. No properties known>
    gap> AppendPointlistToPolymakeObject(permutahedron,points);
    gap> Polymake(permutahedron,"VOLUME");
    3
    gap> Polymake(permutahedron,"N_VERTICES");
    6
          #Now <permutahedron> knows its number of vertices, but not the vertices:
    gap> PropertyOfPolymakeObject(permutahedron,"VERTICES");
    fail
    gap> NamesKnownPropertiesOfPolymakeObject(permutahedron);
    [ "VOLUME", "N_VERTICES" ]
        #Let's look at the object!
    gap> Polymake(permutahedron,"VISUAL");
    #I  There was no or wrong polymake output
    fail
    gap> Polymake(permutahedron,"DIM");
    2
    ]]>
    </Example>

   </Section>

quality100%

¤ Dauer der Verarbeitung: 0.2 Sekunden (vorverarbeitet) ¤

Wurzel

Suchen

Beweissystem der NASA

Beweissystem Isabelle

NIST Cobol Testsuite

Cephes Mathematical Library

Wiener Entwicklungsmethode

Haftungshinweis

Die Informationen auf dieser Webseite wurden nach bestem Wissen sorgfältig zusammengestellt. Es wird jedoch weder Vollständigkeit, noch Richtigkeit, noch Qualität der bereit gestellten Informationen zugesichert.

Bemerkung:

Die farbliche Syntaxdarstellung ist noch experimentell.