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>
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3 changed files with 40 additions and 1 deletions
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@ -144,6 +144,10 @@ fn rule_for<T: Iterator<Item = Token>>(token: &TokenKind) -> ParseRule<T> {
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ParseRule::new(None, Some(Compiler::binary), Precedence::Comparison)
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}
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TokenKind::String(_) => {
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ParseRule::new(Some(Compiler::string), None, Precedence::None)
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},
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_ => ParseRule::new(None, None, Precedence::None),
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}
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}
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@ -255,6 +259,18 @@ impl<T: Iterator<Item = Token>> Compiler<T> {
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Ok(())
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}
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fn string(&mut self) -> LoxResult<()> {
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match &self.previous().kind {
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TokenKind::String(s) => {
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let s = s.clone();
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self.emit_constant(Value::String(s));
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}
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_ => unreachable!("only called for strings"),
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}
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Ok(())
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}
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fn parse_precedence(&mut self, precedence: Precedence) -> LoxResult<()> {
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self.advance();
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let rule: ParseRule<T> = rule_for(&self.previous().kind);
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@ -3,6 +3,7 @@ pub enum Value {
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Nil,
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Bool(bool),
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Number(f64),
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String(String),
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}
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impl Value {
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@ -104,10 +104,32 @@ impl VM {
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);
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}
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OpCode::OpAdd => binary_op!(self, Number, +),
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OpCode::OpSubtract => binary_op!(self, Number, -),
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OpCode::OpMultiply => binary_op!(self, Number, *),
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OpCode::OpDivide => binary_op!(self, Number, /),
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OpCode::OpAdd => {
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let b = self.pop();
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let a = self.pop();
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match (a, b) {
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(Value::String(s_a), Value::String(s_b)) => {
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let mut new_s = s_a.clone();
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new_s.push_str(&s_b);
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self.push(Value::String(new_s));
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}
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(Value::Number(n_a), Value::Number(n_b)) =>
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self.push(Value::Number(n_a + n_b)),
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_ => return Err(Error {
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line: self.chunk.get_line(self.ip - 1),
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kind: ErrorKind::TypeError(
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"'+' operator only works on strings and numbers".into()
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),
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})
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}
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}
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}
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#[cfg(feature = "disassemble")]
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