Caveats

• I'm hoping to talk about colorForth in the large
• I want to talk about the potent ideas in Chuck's explorations
• I have an incomplete view of Chuck's work

Introduction

• Chuck's work has always been about "Decomplexifying"
• Software and hardware is SO complex now
• But kilobytes still matter, and everything is so slow
• We really need to find a better way to write software!
• The ideas in colorForth point the way

Note about Colors

• word - define
• word - compile
• word - execute
• 1234 - execute numbers
• word - variable
• word - force compile
• word - decorate
• word - comment

Note about Colors

• word - define
• word - compile
• word - execute
• 1234 - execute numbers
• word - comment

Don't get distracted by color

• colorForth isn't about syntax highlighting or a neat alternate visualization
• It's not about the eclectic editor
• It's informed by making Forth even simpler

colorForth Chronology

• Precursors (1970-1997)
• iTV Era (1998-20??)
• GreenArrays Era (20??-2015)
• uhdForth (2016-present)

Precursors

What is Forth?

• Highly factored code
• Definitions
• Stacks (to support definitions)

What is a definition?

• : SOME ... ;
• an abbreviation
• should never have more than 1-2 arguments
• stack should never be more than 3-4 deep

You can write FORTRAN in any language

• Forth is powerful, it lets you define any syntax
• There's a temptation to borrow from other languages
• locals, exceptions, structures, scopes, types
• "Find the hundred words to solve you problem in one line."

DEA- FIG,

I AM A FOR-- PRO------- CUR------
EMP----- BY FOR-- INC.  I HAV- NOT
WOR--- ON ANY FIG TYP- SYS---- AND I
AM EXC---- BY THE VAR----- LEN---
NAM- IDE-. PLE--- SEN- ME THE FIG
FOR-- MOD-- SO THA- I MAY TRY IT OUT
HER- AT FOR-- INC.

FRE- THO---- 

DEAR FIG,

I AM A FORTH PROGRAMMER CURRENTLY
EMPLOYED BY FORTH INC.  I HAVE NOT
WORKED ON ANY FIG TYPE SYSTEMS AND I
AM EXCITED BY THE VARIABLE LENGTH
NAME IDEA. PLEASE SEND ME THE FIG
FORTH MODEL SO THAT I MAY TRY IT OUT
HERE AT FORTH INC.

FRED THORTON

DEA- EDI---

I AM AFR--- THA- THE LET--- IN THE LAS- ISS-- ABO--
FOR-- INC- USI-- ONL- THR-- LET--- NAM- FIE--- HAS
HAD THE OPP----- EFF--- FRO- WHA- THE WRI--- WAN---

HIS LET--- ( LIK- THI- ONE ) SHO-- THA- SAV--- ONL-
THR-- LET---- AND COU-- IS JUS- ABO-- OPT---- IN
TER-- OF A TRA-- OFF BET---- SAV--- MEM--- AND
KEE---- LEG--------

YOU-- TRU--
CHU-- MOO--
FOR-- INC-

P.S-  MR. FRE- THO---- IS NOT AN EMP----- OF
      FOR-- INC-

DEAR EDITOR

I AM AFRAID THAT THE LETTER IN THE LAST ISSUE ABOUT
FORTH INC. USING ONLY THREE LETTER NAME FIELDS HAS
HAD THE OPPOSITE EFFECT FROM WHAT THE WRITER WANTED

HIS LETTER ( LIKE THIS ONE ) SHOWS THAT SAVING ONLY
THREE LETTERS AND COUNT IS JUST ABOUT OPTIMAL IN
TERMS OF A TRADE OFF BETWEEN SAVING MEMORY AND
KEEPING LEGIBILITY.

YOURS TRULY
CHUCK MOORE
FORTH INC.

P.S.  MR. FRED THORTON IS NOT AN EMPLOYEE OF
      FORTH INC.

Why was standardizing Forth hard?

• Forth is more complex than it seems
• Dictionary: links, vocabulary hooks, variable length entries
• You can't even define Forth dictionary entries statically in C!
• Fig-Forth had 221 words, not including internals

1993

iTV Era

Early colorForth

• 6 Colored spaces: define, compile, execute, excute number, comment preceed words
• 4 x 3 "stack" of word colors
• Interpret / compile is table dispatch
• square dup * ;

Why is this simpler?

• Compilation and interpretation is more uniform
• How to parse: number / lookup is explicit
• Ambivalence about IMMEDIATE words

      FRAME EMPTY VARIABL
      E BUF W H : ROW A! 1
      59 BEGIN @+ IF + ; T
      HEN DROP NEXT 0 ; RO
      WS DUP BUF ! ROW IF
      DROP DROP ; THEN DRO
      P -1  H +! DUP A + R
      OWS ; 448 H ! VGA 0
      OVER ROWS -1280 SWAP
      640 447 * + ROWS
          

      FRAME EMPTY VARIABL
      E BUF W H : ROW A! 1
      59 BEGIN @+ IF + ; T
      HEN DROP NEXT 0 ; RO
      WS DUP BUF ! ROW IF
      DROP DROP ; THEN DRO
      P -1  H +! DUP A + R
      OWS ; 448 H ! VGA 0
      OVER ROWS -1280 SWAP
      640 447 * + ROWS
          

FRAME EMPTY
VARIABLE BUF W H :
ROW A! 159 BEGIN @+ IF + ; THEN DROP NEXT 0 ;
ROWS DUP BUF ! ROW IF DROP DROP ; THEN
     DROP -1  H +! DUP A + ROWS ;
448 H ! VGA 0
OVER ROWS -1280 SWAP
640 447 * + ROWS
          

Address Registers

• A! - Store to A
• A - Get value of A
• @+ - Read from A and increment
• !+ - Store to A and increment

Less Greedy Conditionals

• IF doesn't consume its argument
• Avoids DUPs
• -IF - Tests sign bit

Simpler flow control

• DO .. LOOP - 2 parameters and just too complicated
• FOR .. NEXT - 1 parameter, good for hardware
• BEGIN .. UNTIL - variable num params
• WORD: ... IF ... WORD ; THEN ... ; - seems to be adequate
• Needs recursive definitions, no smudge
• Tail recursion

GreenArrays Era

Howerd Oakford

• Howerd worked hard to make colorForth easier to run and more accessible
• https://www.inventio.co.uk/cf2023/index.html
• Thanks Howerd!

Example: Fibonacci Numbers

fib ( n--n ) push 1 dup pop -2 +
f ( x...x ) -if drop nip ; then
            push swap over + pop -1 + f ;
8 fib

Example: Fibonacci Numbers

: fib ( n -- n ) >r 1 1 r>
   1- for swap over + next drop nip ;
8 fib

Pre-parsed Words

Shannon Coded Words

Why is this awesome?

• One word = one machine word
• Dispatch is now even more trivial, mask and call
• Parse numbers at edit time
• Dictionary is two arrays

The compiler / interpreter

: eval ( a n -- )
   for
     dup @ dup untag execute 1+
   next drop ;
          

Parts of the system

• dispatcher
• dispatch word per color: number unpacks, define adds to dict, compile adds a call, execute calls
• editor happens beforehand
• seed the dictionary with basic words

Why aren't we all doing this?

• Chuck's implementation doesn't work where we want it
• Which conventions do we adopt?
• Which source conventions do we adopt?

Quirks of "standard" colorForth

• Limitations on name encoding
• Two vocabularies only (forth + macro)
• Definitions drop through
• Literal on execute to compile
• No standard loops
• IF preserves stack
• -IF in place of 0< IF
• No ELSE

MORE Quirks of "standard" colorForth

• >R R> become push pop
• A! A @+ etc.
• @ ! use indexes instead of addresses
• Requires special editor
• Loss of CREATE DOES&rt;
• Unclarity around allocation

Why have I been stuck?

• My RainbowForth was too complex
• I got stuck on trying to match colorForth conventions
• How to sensibly interface with "normal" things?
• Source control, github

Why have I been stuck?

• Subroutine threading is hard
• Color constrains what kind of environment
• Is it a Turing Tar Pit?
• Macro vocabulary or not?
• Can it be even simpler? No compiler, just an editor

uhdForth Era

What is Chuck grappling with?

• Running on Windows
• Avoiding non-explicit macros
• Wants to touch the machine code
• Keeps vacilating on if source is needed

How can we take this somewhere?

• Pick a source format + build something?
• Pick a target? ESP32-colorForth?

What's great with it?

• Editors really are easy to write
• Forth interpreters are harder, less in Forth
• Strings are messy, we haven't found a great vocabulary for them

Proposal

• Try to write simple easy short definititions ;
• Think about how to live without: vocabularies, locals, strings, files, unicode, complexity, CREATE DOES>, objects
• Come back with something useful

flagxor.com
slides

⚘

Thank you