  
  [1m[4m[31m1. Introduction[0m
  
  Groupoids  are  mathematical  categories in which every arrow is invertible.
  The  [1mGpd[0m share package provides functions for the computation with groupoids
  and  their  morphisms;  for  graphs  of  groups and graphs of groupoids. The
  package is far from complete, and development continues.
  
  It  was used by Emma Moore in her thesis [M01] to calculate normal forms for
  Free  Products  with  Amalgamation, and for HNN-extensions, when the initial
  groups have rewrite systems.
  
  [1mGpd[0m  is  implemented  using {\GAP}~4.4. Some of the utility functions in the
  [1mXMod[0m share package for crossed modules are used.
  
  The  information  parameter  [22m[32mInfoGpd[0m  takes  default  value [22m[32m1[0m which, for the
  benefit of new users, causes more messages to be printed out when operations
  fail. When raised to a higher value, additional information is printed out.
  
  Help is available in the usual way.
  
  [22m[35m---------------------------  Example  ----------------------------[0m
    [22m[35m[0m
    [22m[35mgap> LoadPackage( "gpd" );[0m
    [22m[35m------------------------------------------------------------[0m
    [22m[35mloading XMod 2.007 for GAP 4.4 - Murat Alp and Chris Wensley[0m
    [22m[35m------------------------------------------------------------[0m
    [22m[35m-----------------------------------------------------------[0m
    [22m[35mloading Gpd 1.01 for GAP 4.4 - Emma Moore and Chris Wensley[0m
    [22m[35m-----------------------------------------------------------[0m
    [22m[35mtrue[0m
    [22m[35mgap> ?Groupoid[0m
    [22m[35mHelp: several entries match this topic - type ?2 to get match [2][0m
    [22m[35m[0m
    [22m[35m[1] Gpd: Groupoid[0m
    [22m[35m[2] loops (not loaded): groupoid[0m
    [22m[35m[3] Gpd: Groupoids[0m
    [22m[35m[4] Gpd: Groupoids: their elements and attributes[0m
    [22m[35m[5] Gpd: GroupoidByUnion[0m
    [22m[35m[6] Gpd: GroupoidElement[0m
    [22m[35m[7] Gpd: GroupoidMorphismByComponents[0m
    [22m[35m[8] Gpd: GroupoidMorphism[0m
    [22m[35m[9] Gpd: GroupoidsOfGraphOfGroupoids[0m
    [22m[35m[0m
  [22m[35m------------------------------------------------------------------[0m
  
  You may reference this package by mentioning [BM+02] and [M01].
  
