<Section Label="creatingPolymakeObjects"><Heading>Creating Polymake Objects</Heading> The interaction with the polymake program is done via files. So a <K>PolymakeObject</K> is mainly a pointer to a file and a list of known properties of the object. These properties need not be stored in the file. Whenever polymake is called, the returned value is read from standard output and stored in the <K>PolymakeObject</K> corresponding to the file for which polymake is called. <ManSection> <Meth Name="CreateEmptyFile" Arg="filename" /> <Returns>nothing</Returns> <Description> Creates an empty file with name <A>filename</A>. Note that <A>filename</A> has to include the full path and the directory for the file must exist. </Description> </ManSection> <ManSection> <Meth Name="CreatePolymakeObject" Arg=""/> <Meth Name="CreatePolymakeObject" Arg="appvertyp"/> <Meth Name="CreatePolymakeObject" Arg="dir"/> <Meth Name="CreatePolymakeObject" Arg="dir appvertyp"/> <Meth Name="CreatePolymakeObject" Arg="prefix, dir"/> <Meth Name="CreatePolymakeObject" Arg="prefix dir appvertyp"/> <Returns><K>PolymakeObject</K></Returns> <Description> If called without arguments, this method generates an empty file in the directory defined by <Ref Var="POLYMAKE_DATA_DIR"/>. If a directory <A>dir</A> is given (this directory must exist), an empty file is generated in this directory. If <A>prefix</A> is not given, the file is called <F>polyN</F> where <K>N</K> is the current runtime. If a file of this name already exists, a number is appended separated by a dot (example: "poly1340" and "poly1340.1"). If <A>prefix</A> is given, the filename starts with this prefix. Optionally, the file can be generated with a header specifying application, version and type of the object. This is done by passing the triple of strings <A>appvertyp</A> to <Ref Meth="CreatePolymakeObject"/>. A valid triple is <C>["polytope","2.3","RationalPolytope"]</C>. Validity is checked by <Ref Meth="CheckAppVerTypList"/>. </Description> </ManSection> <ManSection> <Meth Name="CheckAppVerTypList" Arg="appvertyp"/> <Returns><K>bool</K></Returns> <Description> Checks if the triple <A>arppvertyp</A> of strings specifies an application and type of polymake version 2.3. More specifically, the first entry has to be an application from <C>["polytope","surface","topaz"]</C> and the third entry has to be a type corresponding to the application given in the first entry. The second entry is not checked.<Br/> </Description> </ManSection> <ManSection> <Meth Name="CreatePolymakeObjectFromFile" Arg="filename"/> <Meth Name="CreatePolymakeObjectFromFile" Arg="dir filename"/> <Returns><K>PolymakeObject</K></Returns> <Description> This method generates a <K>PolymakeObject</K> corresponding to the file <A>filename</A> in the directory <A>dir</A>. If <A>dir</A> is not given, the <K>POLYMAKE&uscore;DATA&uscore;DIR</K> is used.If no file with name <A>filename</A> exists in <A>dir</A> (or <K>POLYMAKE&uscore;DATA&uscore;DIR</K>, respectively), an empty file is created. Note that the contents of the file do not matter for the generation of the object. In particular, the object does not know any of the properties that might be encoded in the file. The only way to transfer information from files to <K>PolymakeObject</K>s is via <Ref Meth="Polymake"/>. </Description> </ManSection> </Section> <Section Label="accessingProperties"><Heading>Accessing Properties of Polymake Objects</Heading> A <K>PolymakeObject</K> contains information about the directory of its file, the name of its file and about properties calculated by calling <Ref Meth="Polymake"/>. The properties returned by the <K>polymake</K> program are stored under the name <K>polymake</K> assigns to them (that is, the name of the data block in the corresponding file). The following methods can be used to access the information stored in a <K>PolymakeObject</K>. But be careful! All functions return the actual object. No copies are made. So if you change one of the returned objects, you change the <K>PolymakeObject</K> itself. <ManSection> <Meth Name="DirectoryOfPolymakeObject" Arg="poly"/> <Returns>Directory</Returns> <Description> Returns the directory of the file associated with <A>poly</A>. </Description> </ManSection> <ManSection> <Meth Name="FilenameOfPolymakeObject" Arg="poly"/> <Returns>String</Returns> <Description> Returns the name of the file associated with <A>poly</A>. This does only mean the name of the <Emph>file</Emph>, not the full path. For the full path and file name see <Ref Meth="FullFilenameOfPolymakeObject"/> </Description> </ManSection> <ManSection> <Meth Name="FullFilenameOfPolymakeObject" Arg="poly"/> <Returns>String</Returns> <Description> Returns the file associated with the <K>PolymakeObject</K> <A>poly</A> with its complete path. </Description> </ManSection> <ManSection> <Meth Name="NamesKnownPropertiesOfPolymakeObject" Arg="poly"/> <Returns>List of Strings</Returns> <Description> Returns a list of the names of all known properties. This does only include the properties returned by <Ref Meth="Polymake"/>, <C>"dir"</C> and <C>"filename"</C> are not included. If no properties are known, <K>fail</K> is returned. </Description> </ManSection> <ManSection> <Meth Name="KnownPropertiesOfPolymakeObject" Arg="poly"/> <Returns>Record</Returns> <Description> Returns the record of all known properties. If no properties are known, <K>fail</K> is returned. </Description> </ManSection> <ManSection> <Meth Name="PropertyOfPolymakeObject" Arg="poly name"/> <Description> Returns the value of the property <A>name</A> if it is known. If the value is not known, <K>fail</K> is returned. <A>name</A> must be a <K>String</K>. </Description> </ManSection> </Section> <Section Label="Exmaple:createAndAccess"> <Heading>Example: Creating and Accessing Polymake Objects</Heading> Suppose the file <F>/tmp/threecube.poly</F> contains the three dimensional cube in polymake form (as generated by the command line <C>cube /tmp/threecube.poly 3 1</C> ). Now generate a <K>PolymakeObject</K> from this file and call <Ref Meth="Polymake"/> to make the vertices of the cube known to the object. <Example> <![CDATA[ ### suppose we have a polymake file /tmp/threecube.poly ### containing a cube in three dimensions gap> cube:=CreatePolymakeObjectFromFile(Directory("/tmp"),"threecube.poly"); <polymake object. No properties known> gap> FilenameOfPolymakeObject(cube); "threecube.poly" gap> FullFilenameOfPolymakeObject(cube); "/tmp/threecube.poly" #nothing is known about the cube: gap> NamesKnownPropertiesOfPolymakeObject(cube); fail gap> Polymake(cube,"VERTICES"); [ [ -1, -1, -1 ], [ 1, -1, -1 ], [ -1, 1, -1 ], [ 1, 1, -1 ], [ -1, -1, 1 ], [ 1, -1, 1 ], [ -1, 1, 1 ], [ 1, 1, 1 ] ] # Now <cube> knows its vertices: gap> Print(cube); <polymake object threecube.poly. Properties known: [ "VERTICES" ]> gap> PropertyOfPolymakeObject(cube,"VERTICES"); [ [ -1, -1, -1 ], [ 1, -1, -1 ], [ -1, 1, -1 ], [ 1, 1, -1 ], [ -1, -1, 1 ], [ 1, -1, 1 ], [ -1, 1, 1 ], [ 1, 1, 1 ] ] gap> KnownPropertiesOfPolymakeObject(cube); rec( VERTICES := [ [ -1, -1, -1 ], [ 1, -1, -1 ], [ -1, 1, -1 ], [ 1, 1, -1 ], [ -1, -1, 1 ], [ 1, -1, 1 ], [ -1, 1, 1 ], [ 1, 1, 1 ] ] ) ]]> </Example> </Section> <Section Label="WritingToObjects"> <Heading>Writing to Polymake Objects</Heading> To transfer data from &GAP; to polymake, the following methods can be used. But bear in mind that none of these functions test if the resulting polymake file is still consistent. <ManSection> <Meth Name="AppendToPolymakeObject" Arg="poly string"/> <Returns>nothing</Returns> <Description> This appends the string <A>string</A> to the file associated to the <K>PolymakeObject</K> <A>poly</A>. It is not tested if the string is syntactically correct as a part of a polymake file. It is also not tested if the string is compatible with the data already contained in the file. </Description> </ManSection> INEQUALITIES, POINTS and VERTICES can be appended to a polymake object using the following functions: <ManSection> <Meth Name="AppendPointlistToPolymakeObject" Arg="poly pointlist"/> <Returns>nothing</Returns> <Description> Takes a list <A>pointlist</A> of vectors and converts it into a string which represents a polymake block labeled "POINTS". This string is then added to the file associated with <A>poly</A>. The "POINTS" block of the file associated with <A>poly</A> then contains points with leading ones, as polymake uses affine notation. </Description> </ManSection> <ManSection> <Meth Name="AppendVertexlistToPolymakeObject" Arg="poly pointlist"/> <Returns>nothing</Returns> <Description> Does the same as <C>AppendPointlistToPolymakeObject</C>, but with "VERTICES" instead of "POINTS". </Description> </ManSection> <ManSection> <Meth Name="AppendInequalitiesToPolymakeObject" Arg="poly ineqlist"/> <Returns>nothing</Returns> <Description> Just appends the inequalities given in <A>ineqlist</A> to the polymake object <A> poly</A> (with caption "INEQUALITIES"). Note that this does not check if an "INEQUALITIES" section does already exist in the file associated with <A>poly</A>. </Description> </ManSection> <ManSection> <Meth Name="ConvertMatrixToPolymakeString" Arg="name matrix"/> <Returns>String</Returns> <Description> This function takes a matrix <A>matrix</A> and converts it to a string. This string can then be appended to a polymake file via <Ref Meth="AppendToPolymakeObject"/> to form a block of data labeled <A>name</A>. This may be used to write blocks like INEQUALITIES or FACETS. </Description> </ManSection> <ManSection> <Meth Name="ClearPolymakeObject" Arg="poly"/> <Meth Name="ClearPolymakeObject" Arg="poly appvertyp"/> <Returns>nothing</Returns> <Description> Deletes all known properties of the <K>PolymakeObject</K> <A>poly</A> and replaces its file with an empty one. <Br/> If the triple of strings <A>appvertyp</A> specifying application, version and type (see <Ref Meth="CheckAppVerTypList"/>) is given, the file is replaced with a file that contains only a header specifying application, version and type of the polymake object. </Description> </ManSection> There are also methods to manipulate the known values without touching the file of the <K>PolymakeObject</K>: <ManSection> <Meth Name="WriteKnownPropertyToPolymakeObject" Arg="poly name data"/> <Description> Takes the object <A>data</A> and writes it to the known properties section of the <K>PolymakeObject</K> <A>poly</A>. The string <A>name</A> is used as the name of the property. If a property with that name already exists, it is overwritten. Again, there is no check if <A>data</A> is consistent, correct or meaningful. </Description> </ManSection> <ManSection> <Meth Name="UnbindKnownPropertyOfPolymakeObject" Arg="poly name"/> <Description> If the <K>PolymakeObject</K> <A>poly</A> has a property with name <A>name</A>, that property is unbound. If there is no such property, <K>fail</K> is returned. </Description> </ManSection> </Section>