| -*- 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 |
| #<box #f> |
| guile> (box-set! b '(list of values)) |
| guile> b |
| #<box (list of values)> |
| guile> (box-ref b) |
| (list of values) |
| guile> (quit) |
| $ |
| |
