38 lines
No EOL
1.1 KiB
Rust
38 lines
No EOL
1.1 KiB
Rust
use crate::expr::{BinaryOp, Expr, UnaryOp};
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pub struct Evaluator {
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ast: Expr
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}
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impl Evaluator {
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pub fn new(ast: Expr) -> Self {
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Self {
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ast
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}
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}
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fn eval_expr(&self, expr: Expr) -> i64 {
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match expr {
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Expr::Number(n) => n,
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Expr::Unary { op, right } => {
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match op {
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UnaryOp::Neg => -self.eval_expr(*right)
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}
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},
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Expr::Binary { op, left, right } => {
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match op {
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BinaryOp::Add => self.eval_expr(*left) + self.eval_expr(*right),
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BinaryOp::Sub => self.eval_expr(*left) - self.eval_expr(*right),
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BinaryOp::Mul => self.eval_expr(*left) * self.eval_expr(*right),
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BinaryOp::Div => self.eval_expr(*left) / self.eval_expr(*right),
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BinaryOp::Mod => self.eval_expr(*left) % self.eval_expr(*right)
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}
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},
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expr => panic!("can't eval expression: {expr:?}")
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}
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}
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pub fn eval(&self) -> i64 {
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self.eval_expr(self.ast.clone())
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}
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} |