Core primitives

This page lists the VM primitive words.

Core primitives

Syntax	Mnemonic	Opcode	Stack effect	Description
nop	NOP	0	… nop == …	No operation; does nothing.
eval	EVAL	1	[A] eval == a*	Evaluates a quotation, executing its contents.
putc	PUTC	2	n putc == {prints char(n)}	Prints a character given by its numeric code.
getc	GETC	3	getc == n {reads char}	Reads a single character from input and pushes its code.
putn	PUTN	5	n putn == {prints n}	Prints a number to output.
clock	CLOCK	6	clock == n {reads clock}	Returns the current time as a Unix timestamp.
drop	DROP	8	a drop ==	Removes the top value from the stack.
q<	PUSHR	14	a q< == | …a	Pushes a value onto the return stack.
q>	PULLR	15	q> == a | a…	Pops a value from the return stack onto the main stack.
<<	SHIFTL	16	a b << == n	Left-shifts a by b bits.
>>	SHIFTR	17	a b >> == n	Right-shifts a by b bits.
clr	CLR	24	… clr ==	Clears the entire stack.
rand	RAND	26	n rand == r {0 <= r < n}	Generates a random number between 0 and n-1.
exit	EXIT	27	n exit == {exits with code n}	Exits the program with the given exit code.
dup	DUP	33	a dup == a a	Duplicates the top value on the stack.
depth	DEPTH	35	… depth == … n	Pushes the current stack depth.
swap	SWAP	36	a b swap == b a	Swaps the top two values on the stack.
%	MOD	37	a b % == a%b	Computes the remainder of a divided by b.*
&	AND	38	a b & == a&b	Bitwise AND of a and b.
(	STASH	40	… ( == {moves stack to queue}	Moves values from the stack to the queue.
)	FETCH	41	) == … {restores stack from queue}	Moves values from the queue back to the stack.
*	MUL	42	a b * == a*b	Multiplies a by b.
+	ADD	43	a b + == a+b	Adds a and b together.
cons	CONS	44	x y cons == q	Builds an anonymous quotation from two stack values.
-	SUB	45	a b - == a-b	Subtracts b from a.
.	DUMP	46	… . == … {prints stack}	Prints the entire stack to output.
/	DIV	47	a b / == ⌊a/b⌋₀	Divides a by b using integer division.*
:	MARK	58	n : == {begin definition(n)}	Begins a new word definition with name n.
;	DEF	59	; == {end definition}	Ends the current word definition.
<	LT	60	a b < == flag	Pushes true if a is less than b.
=	EQ	61	a b = == flag	Pushes true if a equals b.
>	GT	62	a b > == flag	Pushes true if a is greater than b.
?	WHEN	63	flag [A] ? == a*	Executes the quotation if flag is true.
[	BRA	91	[ == {begin quotation}	Begins a quotation (anonymous code block).
]	KET	93	] == [A] {end quotation}	Ends a quotation and pushes it to the stack.
^	POW	94	a b ^ == a^b	Computes a raised to the power of b.
|	OR	124	a b | == a|b	Bitwise OR of a and b.
~	NOT	126	a ~ == ~a	Bitwise NOT of a.

* Division note: the language docs define / as integer division truncated toward zero, with % as the matching remainder. That means -3 2 / is -1, not -2, and -3 2 % is -1.