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|
use super::chunk;
use super::errors::*;
use super::opcode::OpCode;
use super::value::Value;
pub struct VM {
chunk: chunk::Chunk,
// TODO(tazjin): Accessing array elements constantly is not ideal,
// lets see if something clever can be done with iterators.
ip: usize,
stack: Vec<Value>,
}
impl VM {
fn push(&mut self, value: Value) {
self.stack.push(value)
}
fn pop(&mut self) -> Value {
self.stack.pop().expect("fatal error: stack empty!")
}
}
macro_rules! with_type {
( $self:ident, $val:ident, $type:pat, $body:expr ) => {
match $val {
$type => $body,
_ => {
return Err(Error {
line: $self.chunk.get_line($self.ip - 1),
kind: ErrorKind::TypeError(format!(
"Expected type {}, but found value: {:?}",
stringify!($type),
$val,
)),
})
}
}
};
}
macro_rules! binary_op {
( $vm:ident, $type:tt, $op:tt ) => {
binary_op!($vm, $type, $type, $op)
};
( $vm:ident, $in_type:tt, $out_type:tt, $op:tt ) => {{
let b = $vm.pop();
let a = $vm.pop();
with_type!($vm, b, Value::$in_type(val_b), {
with_type!($vm, a, Value::$in_type(val_a), {
$vm.push(Value::$out_type(val_a $op val_b))
})
})
}};
}
impl VM {
fn run(&mut self) -> LoxResult<Value> {
loop {
let op = &self.chunk.code[self.ip];
#[cfg(feature = "disassemble")]
chunk::disassemble_instruction(&self.chunk, self.ip);
self.ip += 1;
match op {
OpCode::OpReturn => return Ok(self.pop()),
OpCode::OpConstant(idx) => {
let c = self.chunk.constant(*idx).clone();
self.push(c);
}
OpCode::OpNil => self.push(Value::Nil),
OpCode::OpTrue => self.push(Value::Bool(true)),
OpCode::OpFalse => self.push(Value::Bool(false)),
OpCode::OpNot => {
let v = self.pop();
self.push(Value::Bool(v.is_falsey()));
}
OpCode::OpEqual => {
let b = self.pop();
let a = self.pop();
self.push(Value::Bool(a == b));
}
OpCode::OpLess => binary_op!(self, Number, Bool, <),
OpCode::OpGreater => binary_op!(self, Number, Bool, >),
OpCode::OpNegate => {
let v = self.pop();
with_type!(
self,
v,
Value::Number(num),
self.push(Value::Number(-num))
);
}
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")]
println!("=> {:?}", self.stack);
}
}
}
pub fn interpret(chunk: chunk::Chunk) -> LoxResult<Value> {
let mut vm = VM {
chunk,
ip: 0,
stack: vec![],
};
vm.run()
}
|
