I could have taken it further, but the implementation there is not "real" in the sense that there is no real return-stack, so you can't implement IF-statements using the lower-level primitives.
That said it is a good starting point, and I had some fun doing it. I'd guesstimate it is more of a single weekend project though, rather than longer.
https://github.com/skx/foth/
Here's the thread which has the barebones overview which inspired me:
https://news.ycombinator.com/item?id=13082825
I could have taken it further, but the implementation there is not "real" in the sense that there is no real return-stack, so you can't implement IF-statements using the lower-level primitives.
That said it is a good starting point, and I had some fun doing it. I'd guesstimate it is more of a single weekend project though, rather than longer.