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Fri Mar 2 15:22:12 GMT 2007

a new PF

summary:

- object oriented: objects are functions. each object has a 'syntactic
  representation S' and an 'associated interpreter I'. (the result of
  applying I to S is X, an executable program which acts on a data
  stack.

- the basic composite data structure is a CONS cell.

- composite data is linear: no shared tails.

- the interpreter needs to be written in (a subset of) itself, to
  allow easy portability (to C).


problems:

all the problems are related to the linearity of the language. to make
things workable, some form of shared structure needs to be
implemented. however, this can lead to dangling references.

-> continuations / return stack
-> mutual recursion

if i clean up the semantics such that dangling pointers are allowed in
some form, like 'undefined word', this should be managable. to keep
things fast, this needs to be cacheable: it should be possible to
detect whether an object is live etc..

to rephrase: looks to me that a completely linear language is really
unpractical. how do you tuck away non-linearity so behaviour is still
real-time?

i keep running into the idea of 'switching off the garbage
collector'.. decompose a program into 2 parts: one that uses a
nonlinear language to build a data/code structure, and a second one
that runs the code: trapped inside the brood idea: tethered
metaprogramming.

-> a predictive real-time linear core (linear forth VM + alloc)
-> a low priority nonlinear metaprogrammer (scheme)

together with the smalltalk trick to simulate the real-time linear
core inside the metaprogrammer.

the VM:
- no if..else..then: only quotation and ifte
- no return stack access: use quotation + dip

this can be a lot more general than for next gen PF. i can run this
kind of stuff on a microcontroller too, to have a different
language. one with quotation, and no parsing words.. the idea is to
make the VM as simple as possible: i already have a way to implement a
native forth, maybe the catkit project should be just that: CAT is
that thing that runs on the micro? linear CAT?



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