Forth Interpreters and the C Stack

I haven't been working on my Forth project for a while, but I'm coming back around to it recently, and there are some things I want to change. One of these things is to start using a variation on a technique I saw in the paper "Implementing lazy functional languages on stock hardware: the Spineless Tagless G-machine". In this paper they give a single line interpreter for their machine: "while (TRUE) { cont = (*cont)(); }" which simply calls the function pointer cont, and expects the function to return a new function pointer. This has the advantage of always cleaning the stack up after every function call, preventing it from overflowing or from having to throw it away occasionally.

The plan as of right now is that instead of always returning the next thing to call, the looping interpreter will simply do the action of "next"- it will copy the current IP (Instruction Pointer) onto the return stack, copy W into IP, increment IP, and call the function W points too. All functions will return nothing and the threading will be taken care of for them- they do not have to each have the code of "next" as I've done in the past.

I'm also going to change how the original dictionary is compiled. Before I was doing some pretty tedious manipulation of an array of cells (integers) for some reason. Instead of this, I will use a word struct of fixed length (the name will be a pointer to a character string rather then the string itself- this makes finding the xt of a word easier). I don't know why I didn't do this before, but it should be simpler and cleaner now.

I've been thinking about what I'm going to do for structures in this Forth. I don't want to use objects particularly, so I'm going to be thinking about how to do reasonable algebraic datatypes in Forth. It will probably involve runtime checking of types. I've devised a scheme for doing classes in the Haskell sense which I will post about, but its in the planning stage and I may abandon the idea at any moment.

I'm looking forward to cleaning up the implementation and getting it actually running so I can start exposing hardware functionality and adding threading, interrupts, etc.