https://github.com/drjayvee/goldylox
Lox interpreter
https://github.com/drjayvee/goldylox
interpreter lox ruby
Last synced: 4 days ago
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Lox interpreter
- Host: GitHub
- URL: https://github.com/drjayvee/goldylox
- Owner: drjayvee
- License: mit
- Created: 2025-10-14T13:50:34.000Z (9 months ago)
- Default Branch: main
- Last Pushed: 2026-05-03T18:36:23.000Z (2 months ago)
- Last Synced: 2026-05-03T20:33:06.722Z (2 months ago)
- Topics: interpreter, lox, ruby
- Language: Ruby
- Homepage:
- Size: 130 KB
- Stars: 0
- Watchers: 0
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
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README
# GoldyLox: an interpreter for Lox, written in Ruby
I'm following along with [Robert Nystrom's Crafting Interpreters](https://craftinginterpreters.com) to learn how to
write an interpreter (which still seems magical to me), as well as to learn (more) Ruby and RBS.
# Showcase
Below are a couple of examples to where the Ruby code is just so much more elegant and beautiful than Java.
These put a smile on my face when I wrote them. 😍
### Scanning until the end of the line or file
```java
while (peek() != '\n' && !isAtEnd()) advance();
```
```ruby
advance until peek == "\n" || eof?
```
The Ruby code reads just almost like plain English. Swapping `while` with `until` to flip the condition makes it
crystal clear.
### Resolving a variable's depth
```java
private void resolveLocal(Expr expr, Token name) {
for (int i = scopes.size() - 1; i >= 0; i--) {
if (scopes.get(i).containsKey(name.lexeme)) {
interpreter.resolve(expr, scopes.size() - 1 - i);
return;
}
}
}
```
```ruby
def resolve_local(expr, name)
@scopes.reverse_each.with_index do |scope, i|
if scope.key? name.lexeme
@interpreter.resolve(expr, i)
return
end
end
end
```
Using `reverse_each` makes the intent immediately clear. There's also no need for `scopes.get(i)`.
Replacing `scopes.size() - 1 - i` with just `i` avoids any chance for off-by-one errors.
### Interpreting a call expressions
```java
@Override
public Void visitCallExpr(Expr.Call expr) {
resolve(expr.callee);
for (Expr argument : expr.arguments) {
resolve(argument);
}
return null;
}
```
```ruby
def visit_call(expr)
resolve expr.callee
expr.arguments.each { resolve it }
end
```
I rest my case. ☺️