Luthor Language

An interpreted programming language with Lex Luthor-themed keywords.

Features a a lexer, recursive descent parser, symbol table and interpreter that runs as a visitor dispatch. ...all in a bit over 1k lines of C++.

Compact, readable, not over-engineered.

The name is a pun on "lexer"

Features

• Variables — know x 10
• Arithmetic — +, -, *, / with proper precedence
• Unary negation — -x, -5, -(expr)
• Comparisons — <, >, <=, >=, ==, !=
• Conditionals — suppose/otherwise/end
• Loops — crime (while loops)
• Output — doom (print)

Example Programs

Hello World (sort of)

doom 42

Output: > 42.0

Variables and Arithmetic

know x 10
know y 5
doom x + y * 2

Output: > 20.0

Unary Negation

know x 5
doom -x
doom -(x + 3)

Output: > -5.0 > -8.0

Conditionals

know age 25
suppose age >= 18
    doom 1
end
otherwise
    doom 0
end

Output: > 1.0

Loops

know counter 0
crime counter < 5
    doom counter
    know counter counter + 1
end

Output: > 0.0 > 1.0 > 2.0 > 3.0 > 4.0

Fibonacci Sequence

know i 0
know a 0
know b 1
crime i < 10
    doom a
    know temp b
    know b a + b
    know a temp
    know i i + 1
end

Output: > 0 > 1 > 1 > 2 > 3 > 5 > 8 > 13 > 21 > 34

Building and Running

Build (requires make and clang++):

cd cpp
make

Run:

./luthor source.lut

Source files use the .lut extension by convention — the interpreter doesn't enforce it.

Language Reference

Keywords

• know — variable assignment
• suppose — if statement
• otherwise — else clause
• crime — while loop
• doom — print statement
• end — block terminator

Operators

• Arithmetic: +, -, *, /
• Unary: - (negation)
• Comparison: <, >, <=, >=, ==, !=
• Grouping: (, )

Syntax Rules

• Blocks must end with end
• Expressions use standard precedence (multiplication before addition, etc.)
• Variables are dynamically typed (currently only numbers)
• Whitespace is mostly ignored (except newlines vs spaces)

Essentially all hand-coded: LLM's used for guidance and teaching, a tedious switch statement, and moving the accept methods out of the nodes.