value-flavoured structures (was: Avoid treating the stack as an array)

On 2024-09-15 20:16, Anton Ertl wrote:

Stephen Pelc <stephen@vfxforth.com> writes:

[...]

However, higher level source code has been much
in demand. An example is Nick Nelson's value flavoured structures,
which are of particular merit when converting code from 32 bit to
64 bit host Forths.

 Gforth has worked on 64-bit hosts since early 1996, and I found that
Forth code tends to have fewer portability problems between 32-bit and
64-bit platforms than C code, and that's not just my code, the
applications in appbench and many others are also quite portable.
 A major merit for value-flavoured structures is that you can change
the field size (e.g, from 1 byte to 2 bytes or vice versa) without
changing all the code accessing those fields.  That's independent of
cell size.

Yes, you can change the field size, but only as far as its value occupies the same number of a stack items and the stack is the same.
For example, it's impossible to change n to d, n to r, or vice versa, without changing all the code accessing those fields.
Similar for the word `to` — `to` applies to the words created with `value`, `fvalue`, `2value`. But the source code around `to foo` (and `foo`) depends on the kind of `foo`, so the kind of `foo` cannot be changed without changing the source code around where it is used.
Higher level (more polymorphic) source code in Forth is possible when all values are boxed [1]
[1] <https://en.wikipedia.org/wiki/Boxing_(computer_science)>
--
Ruvim