1. The GAP InterFace to other Computer Algebra Systems (CAS)
  
  Warning:  this  file is under contruction! You can find the documentation in
  the ../README file.
  
  
  1.1 User's manual
  
  1.1-1 IF_Interface
  
  > IF_Interface( conventional_CAS_name, CAS_function_name, List_of_Gap_objects ) function
  
  See   the   ../README  file  for  the  list  of  interfaced  CASes  and  the
  conventional_CAS_name's.  CAS_function_name  is  the name of the function in
  the  interfaced CAS, and is given as a string. List_of_Gap_objects is a list
  of  Gap  objects,  O_1,  O_2,  ...,  O_n,  that will be used as arguments of
  CAS_function_name (it may be empty).
  
  IF_Interface does the following:
  a.  converts  each object O_1, O_2, ..., O_n in List_of_Gap_objects into the
  corresponding object P_1, P_2, ..., P_n, of the interfaced CAS;
  b.  sends  the  command  CAS_function_name  (  P_1,  P_2,  ..., P_n ) to the
  interfaced CAS;
  c. gets the output from the interfaced CAS;
  d. converts it to the corresponding Gap object, and returns it to the user.
  
  With  the code already implemented, the interface can perform, for instance,
  calculation  like  the following from within Gap, using the function primes,
  omega, and nextprime, of Pari/Gp.
  
  ---------------------------  Example  ----------------------------
    IF_Interface( IF_pari_gp, "primes", [10] );
    IF_Interface( IF_pari_gp, "omega", [360] );
    IF_Interface( IF_pari_gp, "nextprime", [119] );
  ------------------------------------------------------------------
  
  In  the  following  example  the  greatest common divisor of 1000 and 360 is
  calculated using each CAS.
  
  ---------------------------  Example  ----------------------------
    IF_Interface( IF_asir, "igcd", [1000, 360] );
    IF_Interface( IF_cocoa, "GCD", [1000, 360] );
    IF_Interface( IF_kash, "IntGcd", [1000,360] );
    IF_Interface( IF_singular, "gcd", [1000, 360] );
    IF_Interface( IF_plural, "gcd", [1000, 360] );
    IF_Interface( IF_pari_gp, "gcd", [1000, 360] );
    IF_Interface( IF_gap, "GcdInt", [1000, 360] );
    IF_Interface( IF_aribas, "gcd", [1000, 360] );
    IF_Interface( IF_mupad, "gcd", [1000, 360] );
    IF_Interface( IF_maple, "gcd", [1000, 360] );
    IF_Interface( IF_macaulay, "gcd", [1000, 360] );
    IF_Interface( IF_mathematica, "GCD", [1000, 360] );
    IF_Interface( IF_yacas, "Gcd", [1000, 360] );
  ------------------------------------------------------------------
  
  This second example shows that it is possible to interface many CASes in the
  same Gap session.
  
  ---------------------------  Example  ----------------------------
    gap> IF_Interface(IF_mupad, "combinat::partitions::list", [4]);
     [ [ 4 ], [ 3, 1 ], [ 2, 2 ], [ 2, 1, 1 ], [ 1, 1, 1, 1 ] ]
    
    gap> IF_Interface(IF_mupad, "combinat::tableaux::list", [[4,2]]);
     [ [ [ 5, 6 ], [ 1, 2, 3, 4 ] ], [ [ 4, 6 ], [ 1, 2, 3, 5 ] ],
       [ [ 3, 6 ], [ 1, 2, 4, 5 ] ], [ [ 2, 6 ], [ 1, 3, 4, 5 ] ],
       [ [ 4, 5 ], [ 1, 2, 3, 6 ] ], [ [ 3, 5 ], [ 1, 2, 4, 6 ] ],
       [ [ 2, 5 ], [ 1, 3, 4, 6 ] ], [ [ 3, 4 ], [ 1, 2, 5, 6 ] ],
       [ [ 2, 4 ], [ 1, 3, 5, 6 ] ] ]
    
  ------------------------------------------------------------------
  
  1.1-2 InfoInterfaces
  
  > InfoInterfaces__________________________________________________info class
  
  The following command
  
  ---------------------------  Example  ----------------------------
    gap> SetInfoLevel( InfoInterfaces, 3 );
  ------------------------------------------------------------------
  
  tells to Gap to print the input and the output of the interfaced CAS; it may
  be  useful  for debugging purposes. This debugging information is suppressed
  by
  
  ---------------------------  Example  ----------------------------
    gap> SetInfoLevel( InfoInterfaces, 0 );
  ------------------------------------------------------------------