kz80_prolog

A Prolog compiler for the Z80 processor, targeting the RetroShield platform.

Features

• Edinburgh Prolog syntax
• Facts and rules (Horn clauses)
• Unification and backtracking
• Arithmetic evaluation (is, +, -, *, /, mod)
• Comparisons (<, >, =<, >=, =:=, =\=)
• Lists with cons cells ([H|T])
• Cut (!) for control flow
• Basic I/O (write, nl)

Usage

# Compile a Prolog program to Z80 binary
kz80_prolog program.pl -o program.bin

# Print AST (for debugging)
kz80_prolog --ast program.pl

# Print tokens (for debugging)
kz80_prolog --tokens program.pl

Example

% family.pl
parent(tom, bob).
parent(bob, pat).

ancestor(X, Y) :- parent(X, Y).
ancestor(X, Z) :- parent(X, Y), ancestor(Y, Z).

?- ancestor(tom, pat).

Architecture

The compiler uses a Simplified Prolog Machine (SPM) approach:

1. Lexer - Tokenizes Prolog source
2. Parser - Builds AST (recursive descent)
3. Analyzer - Classifies variables (permanent/temporary)
4. Compiler - Generates SPM bytecode
5. Code Generator - Produces 8KB ROM image with interpreter

Memory Layout

ROM (8KB):
  0x0000-0x00FF  Startup
  0x0100-0x0EFF  SPM interpreter
  0x0F00-0x13FF  Runtime library
  0x1400-0x1BFF  Compiled bytecode
  0x1C00-0x1FFF  Atom table

RAM (6KB):
  0x2000-0x27FF  Heap
  0x2800-0x2FFF  Trail
  0x3000-0x35FF  Stack
  0x3600-0x37FF  Registers

Building

cargo build --release

Testing

cargo test

License

BSD-3-Clause