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|
use std::collections::HashMap;
use std::fmt::Display;
use crate::ast::{AstVisitor, Expr, Stmt};
use crate::lexer::{Literal, TokenType};
#[derive(Default)]
pub struct AstInterpreter {
memory: HashMap<String, (Value, bool)>,
}
impl AstVisitor<Value> for AstInterpreter {
fn visit_stmt(&mut self, stmt: &Stmt) -> Value {
match stmt {
Stmt::Block(stmts) => {
self.interpret(stmts);
}
Stmt::Expr(expr) => {
self.visit_expr(expr);
}
Stmt::Val { ident, value } => {
let value = self.visit_expr(value);
self.memory.insert(ident.clone(), (value, false));
}
Stmt::Var { ident, value } => {
let value = self.visit_expr(value);
self.memory.insert(ident.clone(), (value, true));
}
Stmt::Assignment { ident, value } => {
if !self.memory.contains_key(ident) {
panic!("Cannot assign to variable that doesn't exist");
}
if !self.memory[ident].1 {
panic!("Cannot mutate value '{ident}'");
}
let value = self.visit_expr(value);
self.memory.insert(ident.clone(), (value, true));
}
Stmt::Function {
ident: name,
arguments,
return_type,
body,
} => todo!(),
Stmt::If { condition, body } => {
let result = self.visit_expr(condition);
if result == Value::Bool(true) {
self.interpret(body);
}
}
Stmt::For {
binding,
range,
body,
} => todo!(),
Stmt::Return { value } => todo!(),
Stmt::Print { value } => {
println!("{}", self.visit_expr(value));
}
};
// FIXME: Honestly should probably abandon this "visitor" pattern. 2 functions
// with these match statements would work better
Value::Nil
}
fn visit_expr(&mut self, expr: &Expr) -> Value {
match expr {
Expr::Literal(literal) => match literal {
Literal::String(value) => Value::String(value.clone()),
Literal::Character(value) => Value::String(value.to_string()),
Literal::Number(value) => Value::Number(*value),
Literal::Bool(value) => Value::Bool(*value),
Literal::Nil => Value::Nil,
},
Expr::Variable(ident) => self.memory.get(ident).unwrap().clone().0,
Expr::Grouping(child) => self.visit_expr(child),
Expr::Binary { operator, lhs, rhs } => {
let lhs = self.visit_expr(lhs);
let rhs = self.visit_expr(rhs);
if let Value::Number(lhs) = lhs && let Value::Number(rhs) = rhs {
match operator {
TokenType::Plus => Value::Number(lhs + rhs),
TokenType::Minus => Value::Number(lhs - rhs),
TokenType::Star => Value::Number(lhs * rhs),
TokenType::Slash => Value::Number(lhs / rhs),
TokenType::Perc => Value::Number(lhs % rhs),
TokenType::Gt => Value::Bool(lhs > rhs),
TokenType::GtEq => Value::Bool(lhs >= rhs),
TokenType::Lt => Value::Bool(lhs < rhs),
TokenType::LtEq => Value::Bool(lhs <= rhs),
TokenType::BangEq => Value::Bool(lhs != rhs),
TokenType::EqEq => Value::Bool(lhs == rhs),
_ => panic!(),
}
} else if let Value::Bool(lhs) = lhs && let Value::Bool(rhs) = rhs {
match operator {
TokenType::AmpAmp => Value::Bool(lhs && rhs),
TokenType::PipePipe => Value::Bool(lhs || rhs),
_ => panic!()
}
} else if let Value::String(lhs) = lhs && let Value::String(rhs) = rhs {
match operator {
TokenType::Plus => {
let mut value = lhs;
value.push_str(&rhs);
Value::String(value)
},
TokenType::BangEq => Value::Bool(lhs != rhs),
TokenType::EqEq => Value::Bool(lhs == rhs),
_ => panic!()
}
} else {
panic!("Invalid operations for types");
}
}
Expr::Unary { operator, expr } => {
let value = self.visit_expr(expr);
match operator {
TokenType::Bang => {
let Value::Bool(value) = value else {
panic!("Invalid operations for types");
};
Value::Bool(!value)
}
TokenType::Plus => value,
TokenType::Minus => {
let Value::Number(value) = value else {
panic!("Invalid operations for types");
};
Value::Number(-value)
}
_ => panic!(),
}
}
_ => unimplemented!("{:?}", expr),
}
}
}
impl AstInterpreter {
pub fn interpret(&mut self, stmts: &Vec<Stmt>) {
for stmt in stmts {
self.visit_stmt(stmt);
}
}
}
#[derive(Debug, Clone, Eq, PartialEq)]
pub enum Value {
Number(i32),
String(String),
Bool(bool),
Nil,
}
impl Display for Value {
fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
match self {
Value::Number(value) => write!(f, "{value}")?,
Value::String(value) => write!(f, "{value}")?,
Value::Bool(value) => write!(f, "{value}")?,
Value::Nil => write!(f, "nil")?,
}
Ok(())
}
}
#[cfg(test)]
mod test {
//
}
|
