# This tries to create a virtual machine, a virtual machine
# which will be particular suited for the task of parsing
# and compiling.
#
# The machine consists or a stack, a tape, and a work area.
# The stack is manipulated with "push" and "pop", the tape with
# "get" and "put", and the workarea is affected by the 
# "clear" and "add" commands.
#
# Also, the machine includes a pointer which can be manipulated
# explicitly with the "+1;" (etc) commands, and which is 
# affected implicitly with the push and pop commands. In the following
# text, the machine implements itself in the c language.
#
# get - places the contents of the current item of the tape into
#       the work area. The current item of the tape is the item
#       to which the pointer is currently pointing
# put - writes the contents of the work-area to the current item
#       of the tape.
# push  
#   pushes the contents of the work-area onto the stack. Also
#   the tape pointer is incremented by one.
# pop 
#   pops the last item of the stack into the work-area. The 
#   tape pointer is decremented by one.
# clear     
#   deletes the contents of the work-area.
# add 
#   adds the specified text to the text contained in the work-area.
# +n 
#   increments the tape pointer by n places.
# -n 
#   decrements the tape pointer by n places.
# print
#   prints the contents of the work-area to the standard output. 
#
# The tape of the virtual machine is conceived as suitable
# for containing the "attributes" of the tokens as the grammar is being 
# parsed. For example, the attribute of the "add" command is
# the text which follows the command and which will be added to the 
# work-area. The stack of the virtual machine is designed to hold the
# tokens as the are encountered in the lexified input stream. 
# This virtual machine is somewhat inspired by the stream-editor program
# sed, which also can be viewed as a simple virtual machine. The 
# machine is designed to allow the implementation of certain types 
# of grammars and uses right-reduction parsing.
#
# The machine assumes that the input-stream has already been tokenised
# or lexed.

+1;
pop; pop;

/|Word|Semi-Colon/
{
  clear; 
  get;
  +1;
  /pop/
  {
    clear;
    add "pointer--;";
    add "sWorkArea =";
    add "aaTokenStack(pointer);";
  }
  put;
  push;
}

pop;

/|Word|String|Semi-Colon/
{
  clear;
  get;
  /add/
  {
    clear;
    add "sWorkArea = sWorkArea +";
    +1;
    get;
    -1;
    add ";";
    put; clear; put;
  }

  /print/
  {
    clear;
    +1;
  }

}

pop;

/|Pattern|Left-Brace|Command-List|Right-Brace/
{
  clear;
}