Implementing a Forth

a year ago

The author shares their experience with implementing Forth, emphasizing the learning opportunities it provides about concatenative programming and computer operations.
Three approaches to implementing Forth are suggested: porting an existing Forth (like JONESFORTH), creating an ultra-tiny Forth core (examples include PlanckForth, SmithForth, sectorforth, milliForth, StoneKnifeForth, and a 'Three Instruction' Forth), and designing a Forth around a tiny target program (like Meow5 and Snobol4th).
Porting existing Forth implementations is highlighted as a valuable learning method, with the author's own experience porting JONESFORTH to NASM as an example.
The concept of minimal Forth cores is explored, discussing how few words are needed to bootstrap the rest of the language, with examples of extremely compact Forth implementations.
The idea of targeting a specific program to guide Forth implementation is presented, with examples like Meow5 and a SNOBOL4-based Forth that runs a '99 Bottles of Beer' program.
Resources for aspiring Forth implementers are recommended, including JonesForth source, Brad Rodriguez's Moving Forth series, and the book Threaded Interpretive Languages by R.G. Loeliger.

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