Library: define named slots in bulk

[ruv]

By a slot I mean a memory location reserved for some data type, and for which the getter and setter words are defined.

Many years I use slots instead of VALUEs and DEFERs. A one difference is that you have separate individual words to set (or get) a value instead of use the special words like to, is, or action-of. And a second useful thing is that you can create a number of slots at once.

One advantage of setters is that a setter can be easily redefined/wrapped, but a word for which "TO name run-time" semantics are defined cannot be redefined.

In my case, the slots were defined in ForthML — which is an XML-based representation/syntax for Forth.

Now I have prepared a library in standard Forth.

Usage example:

\ create three single-cell slots
slot( n1 n2 n3 ) 

11 set-n1  33 set-n3
n1 . n3 . \ prints "11 33"

\ redefine a setter
: set-n1 dup 0< abort" wrong value for n1" set-n1 ;

12 ' set-n1 catch . \ it prints 0 — no errors
-12 ' set-n1 catch . drop \ it prints a throw code "-2"

\ create two double-cell slots
slot2( d1 sd1 )
123 0  set-d1
0 1 d1 d+ swap . . \ prints "123 1"

\ create two vectors
vect( dothis dothat )

[: ." (this is done)" ;] is-dothis
[: ." (that is done)" ;] is-dothat

dothis dothat \ prints "(this is done)(that is done)"
of-dothis is-dothat
dothat \ prints "(this is done)"

When a slot definition is used inside a definition, creating of slots is postponed.

: create-slot-a-b-c  slot( a b c )  ;
\ the slots are not created yet
create-slot-a-b-c   \ now they are created in the compilation word list
    \ (which can distinct from the word list where "create-slot-a-b-c" is defined)

Feedback is welcome.

[ruv]

Now a syntax to set several slots at once, like x1 x2 set( name1 name2 ) is supported.

It works in interpretation state as well as in compilation state:

slot( a b c ) slot2( dd )
: foo
  1 2 10. 3 set( a b dd c )
  a . b . c . dd d. 
; foo \ prints  "1 2 3 10"

And it's implemented in a single word of three lines two lines of code in its body:

: set(    ( "ccc <right-paren>" -- )
  parse-lexeme-till-rparen dup 0= if 2drop exit then
  s" set-" <#-#> ?find-xt >r recurse r> tt-xt
; immediate

BTW, this example also shows that the dual-xt (or dual-nt) approach doesn't provide any usefulness for such cases. It only requires more bloated code without any profit.