  
  [1X1 [33X[0;0YIntroduction[133X[101X
  
  [33X[0;0Y[5XHomalgToCAS[105X  is  one of the core packages of the [5Xhomalg[105X project [tpa22]. But
  as  one  of  the  rather  technical packages, this manual is probably not of
  interest  for  the  average  uers.  The average user will usually not get in
  direct contact with the operations provided by this package.[133X
  
  [33X[0;0YQuoting  from  the  Appendix  [14X'homalg: The Core Packages and the Idea behind
  their Splitting'[114X of the [5Xhomalg[105X package manual (--> [14X'homalg: HomalgToCAS'[114X):[133X
  
  [33X[0;0Y[21XThe  package  [5XHomalgToCAS[105X (which needs the [5Xhomalg[105X package) includes all what
  is  needed to let the black boxes used by [5Xhomalg[105X reside in external computer
  algebra  systems.  So  as mentioned above, [5XHomalgToCAS[105X is the right place to
  declare   the  three  [5XGAP[105X  representations  external  rings,  external  ring
  elements,  and external matrices. Still, [5XHomalgToCAS[105X is independent from the
  external  computer  algebra  system  with  which  [5XGAP[105X  will  communicate [13Xand[113X
  independent of how this communication physically looks like.[121X[133X
  
  
  [1X1.1 [33X[0;0Y[5XHomalgToCAS[105X[101X[1X provides ...[133X[101X
  
  [30X    [33X[0;6YDeclaration and construction of[133X
  
        [30X    [33X[0;12Yexternal   objects  (which  are  pointers  to  data  (rings,ring
              elements, matrices, ...) residing in external systems)[133X
  
        [30X    [33X[0;12Yexternal rings (as a new representation for the [5XGAP4[105X-category of
              homalg rings)[133X
  
        [30X    [33X[0;12Yexternal   ring  elements  (as  a  new  representation  for  the
              [5XGAP4[105X-category of homalg ring elements)[133X
  
        [30X    [33X[0;12Yexternal matrices (as a new representation for the [5XGAP4[105X-category
              of homalg matrices)[133X
  
  [30X    [33X[0;6Y[10XLaunchCAS[110X:  the  standard  interface used by [5Xhomalg[105X to launch external
        systems[133X
  
  [30X    [33X[0;6Y[10XTerminateCAS[110X:  the  standard  interface  used  by  [5Xhomalg[105X to terminate
        external systems[133X
  
  [30X    [33X[0;6Y[10XhomalgSendBlocking[110X:  the  standard  interface  used  by [5Xhomalg[105X to send
        commands to external systems[133X
  
  [30X    [33X[0;6YExternal  garbage  collection: delete the data in the external systems
        that became obsolete for [5Xhomalg[105X[133X
  
  [30X    [33X[0;6Y[10XhomalgIOMode[110X: decide how much of the communication you want to see[133X
  
