examples/box/README

   1                                                                -*- text -*-
   2
   3 This directory includes an example program for extending Guile with a
   4 new (and even useful) data type.
   5
   6 To build the example, simply type
   7
   8   make box
   9
  10 in this directory.
  11
  12 The resulting `box' program is a Guile interpreter which has one
  13 additional data type called `box'.
  14
  15 A box is simply an object for storing one other object in.  It can be
  16 used for passing parameters by reference, for example.  You simply
  17 store an object into a box, pass it to another procedure which can
  18 store a new object into it and thus return a value via the box.
  19
  20 Box objects are created with `make-box', set with `box-set!' and
  21 examined with `box-ref'.  See the following example session for usage
  22 details:
  23
  24 $ ./box
  25 guile> (define b (make-box))
  26 guile> b
  27 #<box #f>
  28 guile> (box-set! b '(list of values))
  29 guile> b
  30 #<box (list of values)>
  31 guile> (box-ref b)
  32 (list of values)
  33 guile> (quit)
  34 $