| -*- outline -*- | |
| * Overview | |
| This directory includes an example program for extending Guile with a | |
| new (and even useful) data type. | |
| * 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'. See the following example session for usage | |
| details: | |
| ** Example Session | |
| $ ./box | |
| guile> (define b (make-box)) | |
| guile> b | |
| #<box #f> | |
| guile> (box-set! b '(list of values)) | |
| guile> b | |
| #<box (list of values)> | |
| guile> (box-ref b) | |
| (list of values) | |
| guile> (quit) | |
| $ | |