Mise en place formelle du visiteur et séparation de l'affichage d'un arbre syntaxique abstrait (AST).

src/astprinter.rs

@@ -0,0 +1,42 @@
+use crate::expr::{Binary, Expr, ExprVisitor, Grouping, Literal, Unary, VisitableExpr};
+
+pub struct ASTPrinter;
+
+impl ExprVisitor for ASTPrinter {
+    fn visit_binary(&self, b: &Binary) {
+        print!("( {}", b.operator.literal);
+        b.left.accept(self);
+        b.right.accept(self);
+        print!(")");
+    }
+
+    fn visit_grouping(&self, g: &Grouping) {
+        print!("( group ");
+        g.expression.accept(self);
+        print!(")");
+    }
+
+    fn visit_literal(&self, l: &Literal) {
+        match l {
+            Literal::LiteralNumber(i) => print!("{}", i),
+            Literal::LiteralString(s) => print!("{}", s),
+            Literal::LiteralBool(b) => print!("{}", b),
+            Literal::LiteralNil => print!("nil"),
+        }
+    }
+
+    fn visit_unary(&self, u: &Unary) {
+        print!("( {}", u.operator.literal);
+        u.right.accept(self);
+        print!(")");
+    }
+
+    fn visit_expr(&self, e: &Expr) {
+        match e {
+            Expr::BinaryExpr(b) => { b.accept(self); }
+            Expr::GroupingExpr(g) => { g.accept(self); }
+            Expr::LiteralExpr(l) => { l.accept(self); }
+            Expr::UnaryExpr(u) => { u.accept(self); }
+        }
+    }
+}

src/expr.rs

@@ -29,53 +29,44 @@ pub enum Expr {
     UnaryExpr(Unary),
 }
 
-pub trait Visitable {
-    fn visit(&self);
+pub trait ExprVisitor {
+    fn visit_binary(&self, b: &Binary);
+    fn visit_grouping(&self, g: &Grouping);
+    fn visit_literal(&self, l: &Literal);
+    fn visit_unary(&self, u: &Unary);
+    fn visit_expr(&self, e: &Expr);
 }
 
-impl Visitable for Binary {
-    fn visit(&self) {
-        print!("( {}",&self.operator.literal);
-        &self.left.visit();
-        &self.right.visit();
-        print!(")");
+pub trait VisitableExpr {
+    fn accept(&self, visitor: &impl ExprVisitor);
+}
+
+impl VisitableExpr for Binary {
+    fn accept(&self, visitor: &impl ExprVisitor) {
+        visitor.visit_binary(self);
     }
 }
 
-impl Visitable for Grouping {
-    fn visit(&self) {
-        print!("( group ");
-        &self.expression.visit();
-        print!(")");
+impl VisitableExpr for Grouping {
+    fn accept(&self, visitor: &impl ExprVisitor) {
+        visitor.visit_grouping(self);
     }
 }
 
-impl Visitable for Literal {
-    fn visit(&self) {
-        match &self {
-            Literal::LiteralNumber(i) => print!("{}", i),
-            Literal::LiteralString(s) => print!("{}", s),
-            Literal::LiteralBool(b) => print!("{}", b),
-            Literal::LiteralNil => print!("nil"),
-        }
-    }
-}
-
-impl Visitable for Unary {
-    fn visit(&self) {
-        print!("( {}",&self.operator.literal);
-        &self.right.visit();
-        print!(")");
+impl VisitableExpr for Literal {
+    fn accept(&self, visitor: &impl ExprVisitor) {
+        visitor.visit_literal(self);
     }
 }
 
-impl Visitable for Expr {
-    fn visit(&self) {
-        match &self {
-            Expr::BinaryExpr(b) => { b.visit(); }
-            Expr::GroupingExpr(g) => { g.visit(); }
-            Expr::LiteralExpr(l) => { l.visit(); }
-            Expr::UnaryExpr(u) => { u.visit(); }
+impl VisitableExpr for Unary {
+    fn accept(&self, visitor: &impl ExprVisitor) {
+        visitor.visit_unary(self);
     }
 }
+
+impl VisitableExpr for Expr {
+    fn accept(&self, visitor: &impl ExprVisitor) {
+        visitor.visit_expr(self);
+    }
 }

src/main.rs

@@ -1,17 +1,20 @@
 use std::env;
 use std::process;
-use crate::expr::{Binary, Expr, Grouping, Literal, Unary, Visitable};
-use crate::expr::Expr::LiteralExpr;
 
 mod rlox_interpreter;
+
 mod scanner;
 mod token;
 mod token_type;
 mod expr;
+mod astprinter;
 
 use crate::rlox_interpreter::RLoxInterpreter;
 use crate::token::Token;
 use crate::token_type::TokenType;
+use crate::expr::{Binary, Expr, Grouping, Literal, Unary, VisitableExpr};
+use crate::expr::Expr::LiteralExpr;
+use crate::astprinter::ASTPrinter;
 
 // Exit codes from #include <sysexits.h>
 const EX_OK: i32 = 0;
@@ -44,7 +47,7 @@ fn essai_visitor() {
                 line: 0,
                 literal: String::from("-")
             },
-            right: Box::new(Expr::LiteralExpr(Literal::LiteralNumber(123.0)))
+            right: Box::new(Expr::LiteralExpr(Literal::LiteralNumber(456.0)))
         })),
         operator: Token {
             token_type: TokenType::Star,
@@ -57,7 +60,8 @@ fn essai_visitor() {
         }))
     });
 
-    expression.visit();
+    let a = ASTPrinter{};
+    expression.accept(&a);
 }