56.1 RequirePackage

RequirePackage( name )

RequirePackage will try to initialize the share library name. If the package name is not installed at your site RequirePackage will signal an error. If the package name is already initialized RequirePackage simply returns without any further actions.

    gap> CartanMat( "A", 4 );
    Error, Variable: 'CartanMat' must have a value
    gap> ?CartanMat
    CartanMat ________________________ Root systems and finite Coxeter groups
    
    'CartanMat( <type>, <n> )'
    
    returns the Cartan matrix of Dynkin type  <type> and rank <n>. Admissible
    types are the  strings '"A"',   '"B"',   '"C"',    '"D"',   '"E"',   
    '"F"',    '"G"',   '"H"',   '"I"'.
    
        gap> C := CartanMat( "F", 4 );;
        gap> PrintArray( C );
        [ [   2,  -1,   0,   0 ],
          [  -1,   2,  -1,   0 ],
          [   0,  -2,   2,  -1 ],
          [   0,   0,  -1,   2 ] ]
    
    For type  I_2(m),  which is in fact an infinity of types depending on the
    number  m,  a third argument is needed specifying  the integer  m  so the
    syntax is in fact 'CartanMat(  "I",  2, <m> )':
    
        gap> CartanMat( "I", 2, 5 );
        [ [ 2, E(5)^2+E(5)^3 ], [ E(5)^2+E(5)^3, 2 ] ]
    
    'CartanMat( <type1>, <n1>, ... , <typek>, <nk> )'
                          
    returns the   direct sum  of   'CartanMat( <type1>, <n1> )',   ldots,
    'CartanMat( <typek>, <nk> )'. One can use as argument a computed list of 
    types by 'ApplyFunc( CartanMat, [ <type1>, <n1>, ... , <typek>, <nk> ] )'.
                          
    This function requires the package  "chevie"  (see "RequirePackage").
                          
    gap> RequirePackage( "Chevie" );
    Error, share library "Chevie" is not installed in
    LoadPackage( name ) called from
    RequirePackage( "Chevie" ) called from
    main loop
    brk> quit;
    gap> RequirePackage( "chevie" );
 
       WELCOME  to  the  CHEVIE  package,  Version 3  (Dec  1996)
 
          Meinolf Geck,  Frank Luebeck,   Gerhard Hiss, 
          Gunter Malle,  Jean Michel, and Goetz Pfeiffer,
              Lehrstuhl D fuer Mathematik, RWTH Aachen,
              IWR der Universitaet Heidelberg,
              University of St. Andrews and
              Universite Paris VII
 
       This replaces the former weyl package. For first help type
 
              ?CHEVIE Version 3 -- a short introduction
 
    gap> CartanMat( "A", 4 );;
    gap> PrintArray( last );
    [ [   2,  -1,   0,   0 ],
      [  -1,   2,  -1,   0 ],
      [   0,  -1,   2,  -1 ],
      [   0,   0,  -1,   2 ] ]

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