feat(tazjin/rlox): Add initial support for strings

... including concatenation.

This diverges significantly from the book, as I'm using std::String
instead of implementing the book's whole heap object management
system.

It's possible that Lox in Rust actually doesn't need a GC and the
ownership model works just fine.

Change-Id: I374a0461d627cfafc26b2b54bfefac8b7c574d00
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2577
Tested-by: BuildkiteCI
Reviewed-by: tazjin <mail@tazj.in>
This commit is contained in:
Vincent Ambo 2021-02-28 22:35:26 +02:00 committed by tazjin
parent 3b33c1bd76
commit 6f600c8300
3 changed files with 40 additions and 1 deletions

View file

@ -144,6 +144,10 @@ fn rule_for<T: Iterator<Item = Token>>(token: &TokenKind) -> ParseRule<T> {
ParseRule::new(None, Some(Compiler::binary), Precedence::Comparison)
}
TokenKind::String(_) => {
ParseRule::new(Some(Compiler::string), None, Precedence::None)
},
_ => ParseRule::new(None, None, Precedence::None),
}
}
@ -255,6 +259,18 @@ impl<T: Iterator<Item = Token>> Compiler<T> {
Ok(())
}
fn string(&mut self) -> LoxResult<()> {
match &self.previous().kind {
TokenKind::String(s) => {
let s = s.clone();
self.emit_constant(Value::String(s));
}
_ => unreachable!("only called for strings"),
}
Ok(())
}
fn parse_precedence(&mut self, precedence: Precedence) -> LoxResult<()> {
self.advance();
let rule: ParseRule<T> = rule_for(&self.previous().kind);

View file

@ -3,6 +3,7 @@ pub enum Value {
Nil,
Bool(bool),
Number(f64),
String(String),
}
impl Value {

View file

@ -104,10 +104,32 @@ impl VM {
);
}
OpCode::OpAdd => binary_op!(self, Number, +),
OpCode::OpSubtract => binary_op!(self, Number, -),
OpCode::OpMultiply => binary_op!(self, Number, *),
OpCode::OpDivide => binary_op!(self, Number, /),
OpCode::OpAdd => {
let b = self.pop();
let a = self.pop();
match (a, b) {
(Value::String(s_a), Value::String(s_b)) => {
let mut new_s = s_a.clone();
new_s.push_str(&s_b);
self.push(Value::String(new_s));
}
(Value::Number(n_a), Value::Number(n_b)) =>
self.push(Value::Number(n_a + n_b)),
_ => return Err(Error {
line: self.chunk.get_line(self.ip - 1),
kind: ErrorKind::TypeError(
"'+' operator only works on strings and numbers".into()
),
})
}
}
}
#[cfg(feature = "disassemble")]