Hi, there!
I’ve written semi-toy virtual stack machine (a pipe dream has come true 
). To be honest I did not write it from a clean sheet of paper - I used these lessons as a “cheat sheet”.
No, I’m not Forth programmer (Lord forbid 
), but I think that
- Forth is a gem, without any doubt
- implementing something Forth-like is a good way to learn some other language.
About the implementation itself: of course, it is not a fully-blown one:
$ zig-out/bin/zf
zf> .dict
bye . cr .dict .dstk .rstk .cstk .code dup drop
+ - * / mod = <> > < 0= 0<> 0> 0< max min : ;
if else then do i loop (
zf>
zf> 1 2 3
zf> .dstk
dstk[3] = 0x0000000000000003 <- top
dstk[2] = 0x0000000000000002
dstk[1] = 0x0000000000000001
zf>
But even with this minimalistic set of predefined words we can do something kinda useful:
zf> : τετραγωνίζω dup * . ;
zf> 7 τετραγωνίζω cr
49
zf>
Greek word “τετραγωνίζω” (tetragonizo) means “to square”.
More complicated example:
zf> : divisable-by-three 3 mod 0= ;
zf> : test do i dup divisable-by-three if . else drop then loop cr ;
zf> 30 1 test
3 6 9 12 15 18 21 24 27
That’s it.