Wesley's Forth — REPL

⟐ FORTH

stack-based · zero dependencies · RFC 6455

connecting…

ok>

Examples

2 3 + .

basic arithmetic

: SQUARE DUP * ;

define a word

: FACT ... RECURSE ;

recursive factorial

5 0 DO I . LOOP

DO/LOOP counter

DO ... 2 +LOOP

step by 2

VARIABLE X 42 X ! X @ .

variables

42 CONSTANT ANSWER

constants

IF ... ELSE ... THEN

conditionals

FizzBuzz (1–20)

the classic

Primes < 50 (sieve)

variables + loops

.S — show stack

peek without popping

SEE DOUBLE

decompile a word

WORDS

list vocabulary

Stack Words

DUP ( n -- n n )

DROP ( n -- )

SWAP ( a b -- b a )

OVER ( a b -- a b a )

ROT ( a b c -- b c a )

NIP ( a b -- b )

TUCK ( a b -- b a b )

.S show stack

DEPTH stack depth

>R R> R@ return stack

Control Flow

IF … THEN

IF … ELSE … THEN

BEGIN … UNTIL

BEGIN … WHILE … REPEAT

n lim DO … LOOP

n lim DO … step +LOOP

LEAVE exit loop

RECURSE self-call

Arithmetic

+ - * / MOD /MOD

NEGATE ABS MAX MIN

1+ 1- 2+ 2- 2* 2/

Comparison

= < > <> <= >=

0= 0< 0>

True = -1, False = 0

I/O & Memory

. print TOS

EMIT print char

CR SPACE SPACES

." text" print string

@ ! +! fetch/store

? fetch+print

Commands

WORDS list all words

SEE name decompile

RESET — fresh environment

CLEAR — wipe terminal