-*- outline -*- * Overview This directory includes an example program for extending Guile with a new (and even useful) data type. The `box' program created by this example is nearly identical to the one produced in directory ../box, with one (important) difference: The interpreter in this directory will place all defined primitive procedures in a module called (box-module). That means that this module must be used before the primitives can be accessed. * Build Instructions To build the example, simply type make box in this directory. The resulting `box' program is a Guile interpreter which has one additional data type called `box'. * The Box Data Type A box is simply an object for storing one other object in. It can be used for passing parameters by reference, for example. You simply store an object into a box, pass it to another procedure which can store a new object into it and thus return a value via the box. ** Usage Box objects are created with `make-box', set with `box-set!' and examined with `box-ref'. Note that these procedures are placed in a module called (box-module) and can thus only be accessed after using this module. See the following example session for usage details: ** Example Session $ ./box guile> (use-modules (box-module)) guile> (define b (make-box)) guile> b # guile> (box-set! b '(list of values)) guile> b # guile> (box-ref b) (list of values) guile> (quit) $