Hey @grok. Can you write FORTH using M5 macro processor?

Thought for 1m 0s

Yes, it's possible to implement a Forth interpreter or compiler using a macro processor like M4 (and by extension, its evolutionary successor M5, which shares similar macro expansion and substitution principles). Macro processors excel at text transformation, making them ideal for generating low-level code (e.g., assembly) from high-level Forth definitions. While no public implementation specifically uses Alan Dain Samples' historical M5 (whose source and detailed examples are scarce), a robust example exists using GNU M4 to create a Forth-to-Z80 assembler cross-compiler. This targets the ZX Spectrum but demonstrates the technique: M4 macros define Forth primitives (e.g., stack ops, arithmetic) as Z80 instruction snippets, handling control flow with label counters for uniqueness.M5, as an M4 evolution, would adapt similarly—its enhanced features (e.g., better argument handling and streams) could streamline expansions, but the core approach (defining words as macro substitutions) translates directly. Below, I'll outline how it works, provide key macro definitions, and show a complete example. This generates human-readable, annotated assembly without peephole optimization but with inline efficiencies (e.g., DUP ADD → _2MUL).How It WorksCore Mechanism: Input Forth code (e.g., : FOO DUP ADD ;) is processed by M4. Macros like DUP expand to Z80 code preserving stack effects (data stack in HL/DE/SP; return stack in HL'/DE'/BC'). Labels use counters (e.g., if100) to avoid conflicts.

Stacks: 16-bit data stack; return address stack (RAS) for loops/recursion.

Compilation: m4 input.m4 > output.asm, then assemble (e.g., with Pasmo for Z80).

Adaptation to M5: Use M5's = for definitions (vs. M4's define) and => streams for output diversion. Argument parsing aligns closely.

Limitations: Uppercase words only; 16/32-bit ints; basic floats via ROM.

Key Macro DefinitionsMacros are modular (e.g., in stack.m4, arithmetic.m4). Here's a selection:Stack Manipulation (e.g., from stack.m4):

  define({DUP},{                ; ( x1 -- x1 x1 )
    ex   DE, HL               ; 1:4       dup
    push HL                   ; 1:11      dup})dnl

  define({SWAP},{               ; ( x2 x1 -- x1 x2 )
    ex   DE, HL               ; 1:4       swap})dnl

  define({DROP},{               ; ( x1 -- )
    pop  HL                   ; 1:10      drop
    ex   DE, HL               ; 1:4       drop})dnl

  define({PUSH($1)},{           ; ( -- n )
    push HL                   ; 1:11      push($1)
    ld   HL, $1               ; 3:10      push($1)
    ex   DE, HL               ; 1:4       push($1)})dnl

Optimization Example: DUP DUP → DUP_DUP for fewer instructions:

  define({DUP_DUP},{             ; ( x1 -- x1 x1 x1 )
    exx                       ; 1:4       dup dup
    push HL                   ; 1:11      dup dup
    exx                       ; 1:4       dup dup
    ex   DE, HL               ; 1:4       dup dup
    push HL                   ; 1:11      dup dup})dnl

Arithmetic (e.g., from arithmetic.m4):

  define({ADD},{                ; ( x2 x1 -- x )
    add  HL, DE               ; 1:11      +
    ex   DE, HL               ; 1:4       +
    pop  HL                   ; 1:10      +})dnl

  define({SUB},{                ; ( x2 x1 -- x )
    or   A                    ; 1:4       -
    sbc  HL, DE               ; 2:15      -
    ex   DE, HL               ; 1:4       -
    pop  HL                   ; 1:10      -})dnl

  define({MUL},{                ; ( x2 x1 -- x )  [Binary long multiplication loop]
    push BC                   ; 1:11      *
    ld   B, H                 ; 1:4       *
    ld   C, L                 ; 1:4       *
    ld   HL, 0x0000           ; 3:10      *
    ld   A, 0x10              ; 2:7       *
    mul_loop101:              ;           *
    add  HL, HL               ; 1:11      *
    rl   E                    ; 2:8       *

-- ETC ETC. Rest of assembly pørn censored.

Forth – Is it still relevant?