Cowlang

Cowlang is an esoteric programming language written by User:Treeplate for the second truttle1 practical programming language jam, in February 2025.

Tokens

There are 4 types of tokens.

String

Strings are '-delimited with no escapes.

Integers

Integers are sequences of the following characters: 0123456789. This is required to fit in 63 bits.

Symbols

Symbols are the following characters: []()+-*/%&|^<.

Comments

// denotes the start of a comment, which ends at the first newline (0xa) that isn't preceded by a \.

= Whitespace

Spaces (0x20), tabs (0x9), carriage returns (0xd), and newlines (0xa) are ignored.

Identifiers

Any other character marks the start of an identifier, which ends at a space, tab, carriage return, newline, or any of the following characters: []()+-*/%&|^<.

Parsing

Statements

These tokens are parsed into a set of statements, which are parsed the following way: === Starting with identifier def Parse an identifier (the name).

Next token is (

Parse identifiers until you get to a ) (the parameters). Parse statements until you get to an identifier `end` (the body). The statement is declaring a function.

Next token is <

Parse an expression. The statement is evaluating the expression and assigning it to a new variable.

Starting with identifier if

First, parse an expression (the condition). Then, parse statements until there is an identifier end. (the block). The statement is executing the block only if the condition evaluates to 0.

Starting with identifier loop

First, parse an expression (the condition). Then, parse statements until there is an identifier end. (the block). The statement is repeatedly executing the block until the condition does not evaluate to 0.

Other

First, parse an expression. If that expression is assignable (indexing or variable) and the next token is <, parse another expression. The statement is assigning the second expression to the first expression. Otherwise, the statement is evaluating the expression.

Expressions

The following table lists the precedence of expressions. Expressions are listed top to bottom, in descending precedence. In case of precedence tie, expressions are right-associative. a, b and c are operands.

• a | b (bitwise or)
• a ^ b (bitwise xor)
• a & b (bitwise and)
• a * b (multiply), a / b (divide and floor), a % b (modulus)
• a + b (add), a - b (subtract)
• a[b] (indexing into a list), a(b c) (function call)
• identifiers (variable), strings, and integers

RTL

• print(str) (prints str)
• intToStr(int) (converts int to str)
• random(int) (returns an integer between 0 (incl.) and int (excl.))
• input() (returns line of stdin)
• strToInt(str) (parses str as an integer)
• positive(int) (returns 0 if int is positive and 1 otherwise)
• readFile(str) (reads file str)
• split(str, int) (splits str into a list of strings that are separated by the character int in str)
• length(list) (returns length of list)
• list(int) (returns a list with int zeros)

Examples

Fibonacci

def fib(i) 
 def resultNotAssigned < 0
 if i 
   result < 0 
   resultNotAssigned < 1 
 end
 if 1-i 
   result < 1 
   resultNotAssigned < 1 
 end
 if resultNotAssigned
   result < fib(i-1) + fib(i-2) 
 end
end
print(intToStr(fib(0)))
print(intToStr(fib(1)))
print(intToStr(fib(6)))
print(intToStr(fib(20)))

prints "pass" print('PASS')

Implementation

https://github.com/treeplate/cowlang