chap1.txt

  
  1 The Example Package
  
  This  chapter  describes the GAP package Example. As its name suggests it is
  an  example  of  how  to  create  a GAP package. It has little functionality
  except for being a package.
  
  See  Sections 2.1,  2.2  and 2.3  for  how  to install, compile and load the
  Example package, or Appendix A for guidelines on how to write a GAP package.
  
  If you are viewing this with on-line help, type:
  
    Example  
    gap> ?Example package
  
  
  to see the functions provided by the Example package.
  
  
  1.1 The Main Functions
  
  The following functions are available:
  
  1.1-1 ListDirectory
  
  ListDirectory( [dir] )  function
  
  lists  the  files  in  directory  dir (a string) or the current directory if
  called with no arguments.
  
  1.1-2 FindFile
  
  FindFile( directory_name, file_name )  function
  
  searches   for   the   file  file_name  in  the  directory  tree  rooted  at
  directory_name  and  returns  the  absolute path names of all occurrences of
  this file as a list of strings.
  
  1.1-3 LoadedPackages
  
  LoadedPackages(  )  function
  
  returns  a list with the names of the packages that have been loaded so far.
  All this does is execute
  
    Example  
    gap> RecNames( GAPInfo.PackagesLoaded );
  
  
  You  might  like  to  check out some of the other information in the GAPInfo
  record (see 'Reference: GAPInfo').
  
  1.1-4 Which
  
  Which( prg )  function
  
  returns the path of the program executed if Exec(prg); is called, e.g.
  
    Example  
    gap> Which("date");         
    "/bin/date"
    gap> Exec("date");
    Fri 28 Jan 2011 16:22:53 GMT
  
  
  1.1-5 WhereIsPkgProgram
  
  WhereIsPkgProgram( prg )  function
  
  returns  a  list  of paths of programs with name prg in the current packages
  loaded. Try:
  
    Example  
    gap> WhereIsPkgProgram( "hello" );
  
  
  1.1-6 HelloWorld
  
  HelloWorld(  )  function
  
  executes the C program hello provided by the Example package.
  
  1.1-7 FruitCake
  
  FruitCake global variable
  
  is a record with the bits and pieces needed to make a boiled fruit cake. Its
  fields satisfy the criteria for Recipe (1.1-8).
  
  1.1-8 Recipe
  
  Recipe( cake )  operation
  
  displays  the  recipe  for  cooking  cake, where cake is a record satisfying
  certain  criteria  explained  here: its recognised fields are name (a string
  giving the type of cake or cooked item), ovenTemp (a string), cookingTime (a
  string),  ingredients  (a list of strings each containing an _ which is used
  to line up the entries and is replaced by a blank), method (a list of steps,
  each  of  which  is  a  string  or  list  of  strings), and notes (a list of
  strings).  The global variable FruitCake (1.1-7) provides an example of such
  a string.