A small Forth implementation.

Run make from the root of the repository

From the root of the repository - ./4th

The 4th.conf file is interpreted prior to the REPL running. Any composures created in 4th.conf are avaiable in the REL and any words outside of a composure are executed.

bye

Stack Worlds

dot (a --) Remove the top of the data stack and display it.

drop ( a -- ) Remove the top of the data stack.

dup ( a -- a a ) Duplicate the data stack top.

over ( a b -- a b a ) Duplicate the top-1 (second element) of the data stack and put it on the top.

swap ( a b -- b a ) Duplicate the top of the data stack.

rot ( a b c -- b c a ) Rotate the top 3 elements of the data stack to the left.

Output Words

.s ( -- ) Displays the contents of the data stack.

read ( -- a) Reads a word from stdin and puts it on the data stack.

emit (char -- ) Displays the character

Arithemtic Words

+ ( n1 n2 -- n3 ) Adds n1+n2

- ( n1 n2 -- n3 ) Subtracts n1-n2

* ( n1 n2 -- n3 ) Multiply n1*N2

mod ( n1 n2 -- n3 ) Remainder of n1/n2

Memory Words

variable ( -- ) name Defines a variable

! ( n adr -- ) Stores a number at adr

@ ( adr -- n ) Fetches a number from adr

Composing Words

: ( -- sys ) name Starts the compilation of a new colon definition

; ( -- ) Finishes the compilation of a colon definition

Return Stack Words

>r ( n -- ) Moves a number to the return stack

r> ( -- n ) Moves a number from the return stack to the data stack

r@ ( -- n ) Copies the top of the return stack to the data stack

Lifecycle Management Words

execute ( acf -- ) Executes the word whose compilation address is on the stack

compile ( -- ) Compiles next word at run time

run ( adr -- ) Compiles and executes the string pointed to by the address