UNIX `dc` cheatsheet

dc_cheatsheet.md

DC Cheatsheet

Mathematical operators

Operator	Stack effect	notes
+	a b -- $a+b$
-	a b -- $a-b$
*	a b -- $a*b$
/	a b -- $\frac{a}{b}$
%	a b -- $mod(a,b)$
~	a b -- $\frac{a}{b}$ $mod(a,b)$	a, b only eval'd once. 2 values pushed
^	a b -- $a^b$
v	a -- $\sqrt{a}$
_	a -- $-a$	(underscore) negate value, _5 also ok
b	a -- $\lvert a \rvert$	absolute value
|	a b c -- $a^b (mod \space c)$	modular exponentiation
$	a -- $truncate(a)$	drop fractional part
@	a b -- a	sets a to b digits of precision
H	a b -- $a * 10^b$	shift a b digits left
h	a b -- $a * 10^{-b}$	shift a b digits right

Logical operators

Operator	Stack effect	notes
G	a b -- $a == b$	1 if a equals b, otherwise zero
N	a -- $a == 0$	1 if a is zero, else zero
(	a b -- $a \lt b$	1 if a is less than b, else zero
{	a b -- $a \leq b$	1 if a is less than or equal b, else 0
)	a b -- $a \gt b$	1 if a is greater than b, else zero
}	a b -- $a \geq b$	1 if a is greater than or equal b, else 0
M	a b -- $a \land b$	1 if a and b are nonzero, zero otherwise
m	a b -- $a \lor b$	1 if a or b are nonzero, zero otherwise

Stack manipulation

Operator	Stack effect	notes
c	--	clears the stack
d	a -- a a	duplicates item on top of stack
r	a b -- b a	swaps the top two items
R	a b -- a	Pops the top item from the stack

Register control

A register is named by any single character, r, which follows the operator. Each named register is also its own stack.

Operator	Stack effect	notes
sr	a b -- a (r = b)	pops stack and stores item in register r
lr	a (r = b) -- a b	copies value of r and pushes on the stack
Sr	a c (r = b) -- a (r = b c)	Pops item, pushes onto the r stack
Lr	a (r = b c) -- a c (r = b)	Pops r register, pushes onto main stack