Gotolang

Gotolang is an esoteric programming language written by icitry in which the only instruction is goto + a few more.

Not to be confused with GotoLang which was created first.

See the original source here.

Syntax

• Gotolang programs are line-oriented. Each line contains one instruction. Comments start with #.

# Count from 0 to 4.
set i 0

label loop
lt i 5
if body
goto done

label body
print i
print "\n"
add i 1
goto loop

label done
halt

• Variables are created automatically and default to 0 when first read. Operands are either integer literals or variable names:

set x 10
add x 1
set y x

• Only string literals work for the print statement

print "Hello, World!"

Instructions

Control Flow

Instruction	Description
label <name>	defines a jump target
goto <label>	unconditionally jumps to label
if <label>	conditionally jumps to a label (the line before must contain the condition)
halt	stop the program

Conditions

Instruction	Description
eq <a>	evaluates to true if a == b
lt <a>	evaluates to true if a < b

Data Manipulation

Instruction	Description
set <operand>	sets a variable to a literal or another variable
add <operand>	adds an opperand to a variable
sub <operand>	subtracts an operand from a variable

Input and Output

Instruction	Description
print <operand>	prints operand to STDOUT
read	reads into var from STDIN

Notes

• Identifiers contain letters, digits, and underscores, and cannot start with a digit.
• Integers are signed 64-bit values.
• The comparison flag is overwritten by each eq or lt.
• if <label> means "if the current comparison flag is true, jump to <label>."
• Unknown labels, duplicate labels, and malformed instructions are reported as errors.

Examples

Factorial

print "Enter n: "
read n

set fact 1
set i 1

label loop
lt n i
if done

set old fact
set fact 0
set m 0
label multiply_loop
eq m i
if multiply_done
add fact old
add m 1
goto multiply_loop

label multiply_done
add i 1
goto loop

label done
print "n! = "
print fact
halt

Brainfuck Interpeter

If you're not familiar with the language, see Brainfuck

Due to the limitations of Gotolang, the interpreter has the following restrictions and changes:

• The tape only has 10 cells
• Programs can be no longer than 29 characters long
• The program can only be in intergers

Convertions

Command	Integer Representation
>	0
<	1
+	2
-	3
.	4
,	5
[	6
]	7

Example input that runs ++[>+<-]> :

10
2 2 6 0 2 1 3 7 0 4

Expected output:

2

here's the interpreter

Implementations

By icitry a rust interpreter (look here for more programs)