Objecttypes

HolonTForth implements a simple objecttype mechanism. Objects have private data and access methods that are activated by messages. There is no inheritance, objects are static with early binding. Example: 

Variable

Define: 55 variable var   
Use:    var 5 + .   5 var add   var print   var incr   77 var set   
for Forth freaks also:   var @ 55 * var !   

Messages and methods are separate items. The messages are defined as

Message get
Message set
Message add
...

The corresponding methods are scripts stored in an array for each objecttype. Example:

Objecttype variable 
set variable(instance) {set obj [pop]}  

set variable() {push $obj}   ;# default method
set variable(get) {push $obj}
set variable(@) {push $obj}
set variable(set) {set obj [pop]}
set variable(!) {set obj [pop]}
set variable(incr) {incr obj}
set variable(add) {set obj [expr {$obj+[pop]}]}
set variable(print) {puts -nonewline $obj}

The "instance" method is used when an object is created, it defines the instance data.

If the object is used without a message, the default message () is used.

Several messages call the same action, e.g. get and @, set and !. Choose what you prefer, or add your own!

HolonTForth presently also defines the following objecttypes.

String

Messages: get @ set ! print append index length tolower

Example:  " a little text " string S    
Use: " for you" S append    S print 

Array

Messages: get @ set ! incr add names

Example:  {} array A    
Use:  11 1 A set    
      22 2 A set    
      1 A 2 A +  ( -- 33 )    

List

Messages: index @ get set ! setlist getlist append search revert sort length print
also to use a list as a stack: push pop

Example:  { 11 22 33} list L  
Use: 1 L index ( -- 22 ),  1 L get ( -- 22 ),  1 L ( -- 22 )
     1 L 2 L +  ( -- 55 )
     L getlist ( -- {11 22 33} )
     888 L push   L getlist  ( -- {11 22 33 888} )                           
     L pop  ( -- {11 22 33} 888 ) 

File

Messages: name get put open-w open-r close eof

Example: " source.tcl" file sfile  \ file object 
Use: sfile open-r      
     begin sfile get .cr          \ read a line and print 
           sfile eof 
     until  
     sfile close