What is Opal?

Opal is a stack-based programming language for code golf.

Syntax

All the program memory is contained in a single stack called the program stack. Programs are read by the interpreter one character at a time. Numbers consisting of a single digit are appended to the program stack as is. If you want to add a multidigit number to the program stack, you must end the number with the character @. Anything enclosed in double quotes "" is treated as a string. Any values left in the program stack at the end of the program will be concatenated together and outputted as a single string.

The character q is a special character which takes input from the user and stores it in the program stack. Operators which manipulate the values in the program stack are defined below.

Operators

Operation	Operator	Example program	Example output
Concatenation	@	123@1+	124
Negation	~	3~	-3
Addition	+	34+	7
Subtraction	-	23-	-1
Multiplication	*	23*	6
Division	/	35/	0.6
Modulus	%	53%	2
Power	^	23^	8
Square	#	2#	4
Square root	\	4\	2
Root	r	83r	2
Is greater than?	>	53>	True
Is less than?	<	53<	False
Is equal?	=	44=	True
Ceiling function	(	0.6(	1
Floor function	)	0.6)	0
Absolute value	a	3~a	3
Factorial	!	5!	120
Logarithm base-10	l	2l	0.3010299956639812
Natural logarithm	n	2n	0.6931471805599453
Logarithm	b	82b	3
Pi	p	p	3.141592653589793
e	e	e	2.718281828459045
Sine function	s	ps	0
Cosine function	c	pc	-1
Tangent function	t	pt	0
Is prime?	v	7v	True
Euclidean distance	d	0043d	5
Sign function	S	4~S	-1
# of permutations	P	53P	60
# of combinations	C	53C	10
Greatest common divisor	G	60@48@G	12
Generate random float in [0, 1)	R	R	0.6745571862859855
TRUE	T	T	True
FALSE	F	F	False
Boolean OR	|	TF|	True
Boolean AND	&	TF&	False
Boolean NOT	N	TN	False
Pop top element off program stack	y	"a""b"y	a
Swap top two elements of program stack	;	"a""b";	ba
Duplicate top element of program stack	_	"a"_	aa

Example programs

hello_world

Program: "Hello World!"

Prints "Hello World!"

Output: Hello World!

sum

Program: 12+

Computes sum of 1 and 2

Output: 3

square_root

Program: 9\

Computes square root of 9

Output: 3

distance

Program: 0043d

Computes Euclidean distance between points (0, 0) and (4, 3)

Output: 5

convert_to_fahrenheit

Program: q1.8*32@+

Takes input from the user representing temperature in degrees Celsius. Converts to temperature in degrees Fahrenheit.

Example input: 37.5

Example output: 99.5

random

Program: R10@*)

Generates random integer in [0, 9]

Example output: 6