diff --git a/src/main.rs b/src/main.rs
index 66129a9..5717056 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -7,6 +7,8 @@ mod scanner;
 mod token;
 mod token_type;
 mod expr;
+mod astprinter;
+mod parser;
 
 use crate::rlox_interpreter::RLoxInterpreter;
 
@@ -34,4 +36,4 @@ fn main() {
 // https://github.com/munificent/craftinginterpreters/wiki/Lox-implementations#rust
 
 // Pause :
-// http://www.craftinginterpreters.com/representing-code.html#working-with-trees
+// http://www.craftinginterpreters.com/parsing-expressions.html  implémentation de comparison
diff --git a/src/parser.rs b/src/parser.rs
new file mode 100644
index 0000000..d2e0488
--- /dev/null
+++ b/src/parser.rs
@@ -0,0 +1,215 @@
+use crate::expr::{Binary, Expr, Grouping, Unary};
+use crate::expr::Literal::{LiteralBool, LiteralNumber, LiteralString};
+use crate::token::Token;
+use crate::token_type::TokenType;
+
+pub struct Parser {
+    tokens: Vec<Token>,
+    current: usize
+}
+
+pub struct ParseError {
+    message: String
+}
+
+impl Parser {
+    pub fn new( t_init: Vec<Token >) -> Self {
+        Parser {
+            tokens: t_init,
+            current: 0
+        }
+    }
+
+    fn match_token( &mut self, token_type_list: &[TokenType] ) -> bool {
+        for token_type in token_type_list {
+            if self.check(token_type) {
+                self.advance();
+                return true;
+            }
+        }
+
+        return false;
+    }
+
+    fn check(&self, token_type: &TokenType) -> bool {
+        if self.is_at_end() {
+            return false;
+        }
+
+        return self.peek().token_type==*token_type;
+    }
+
+    fn advance(&mut self) -> Token {
+        if !self.is_at_end() {
+            self.current += 1;
+        }
+        return self.previous();
+    }
+
+    fn is_at_end(&self) -> bool {
+        return self.peek().token_type==TokenType::Eof;
+    }
+
+    fn peek(&self) -> Token {
+        return self.tokens[self.current].clone();
+    }
+
+    fn previous(&self) -> Token {
+        return self.tokens[self.current - 1].clone();
+    }
+
+    fn consume(&mut self, token_type: &TokenType, message: String) -> Result<(), ParseError> {
+        if self.check(token_type) {
+            self.advance();
+            return Ok(());
+        }
+
+        Err(ParseError {
+            message
+        })
+    }
+
+    fn synchronise(&mut self) {
+        self.advance();
+
+        while !self.is_at_end() {
+            if self.previous().token_type == TokenType::Semicolon {
+                return;
+            }
+
+            match self.peek().token_type {
+                TokenType::Class => return,
+                TokenType::Fun => return,
+                TokenType::Var => return,
+                TokenType::For => return,
+                TokenType::If => return,
+                TokenType::While => return,
+                TokenType::Print => return,
+                TokenType::Return => return,
+                _ => (),
+            }
+
+            self.advance();
+        }
+    }
+
+    fn expression(&mut self) -> Result<Expr,ParseError> {
+        self.equality()
+    }
+
+    fn equality(&mut self) -> Result<Expr,ParseError> {
+        let mut expr: Expr = self.comparison()?;
+
+        while self.match_token( &[TokenType::BangEqual, TokenType::EqualEqual]) {
+            let operator: Token = self.previous();
+            let right: Expr = self.comparison()?;
+            expr = Expr::BinaryExpr(Binary{
+                left: Box::new(expr),
+                operator,
+                right: Box::new(right)
+            });
+        }
+
+        return Ok(expr);
+    }
+
+    fn comparison(&mut self) -> Result<Expr,ParseError> {
+        let mut expr = self.term()?;
+
+        while self.match_token(&[TokenType::Greater, TokenType::GreaterEqual, TokenType::Less, TokenType::LessEqual]) {
+            let operator = self.previous();
+            let right = self.term()?;
+            expr = Expr::BinaryExpr(Binary{
+                left: Box::new(expr),
+                operator,
+                right: Box::new(right)
+            });
+        }
+
+        return Ok(expr);
+    }
+
+    fn term(&mut self) -> Result<Expr,ParseError> {
+        let mut expr = self.factor()?;
+
+        while self.match_token(&[TokenType::Minus, TokenType::Plus]) {
+            let operator = self.previous();
+            let right = self.factor()?;
+            expr = Expr::BinaryExpr(Binary{
+                left: Box::new(expr),
+                operator,
+                right: Box::new(right)
+            });
+        }
+
+        return Ok(expr);
+    }
+
+    fn factor(&mut self) -> Result<Expr,ParseError> {
+        let mut expr = self.unary()?;
+
+        while self.match_token(&[TokenType::Star, TokenType::Slash]) {
+            let operator = self.previous();
+            let right = self.unary()?;
+            expr = Expr::BinaryExpr(Binary{
+                left: Box::new(expr),
+                operator,
+                right: Box::new(right)
+            });
+        }
+
+        return Ok(expr);
+    }
+
+    fn unary(&mut self) -> Result<Expr,ParseError> {
+        if self.match_token(&[TokenType::Bang, TokenType::Minus]) {
+            let operator = self.previous();
+            let right = self.unary()?;
+            return Ok(Expr::UnaryExpr(Unary {
+                operator,
+                right: Box::new(right)
+            }));
+        }
+
+        self.primary()
+    }
+
+    fn primary(&mut self) -> Result<Expr,ParseError> {
+        if self.match_token(&[TokenType::False]) {
+            return Ok(Expr::LiteralExpr(LiteralBool(false)));
+        }
+        if self.match_token(&[TokenType::True]) {
+            return Ok(Expr::LiteralExpr(LiteralBool(true)));
+        }
+        if self.match_token(&[TokenType::Nil]) {
+            return Ok(Expr::LiteralExpr(LiteralBool(false)));
+        }
+        if self.match_token(&[TokenType::Number]) {
+            return Ok(Expr::LiteralExpr(LiteralNumber(self.previous().literal.parse::<f64>().unwrap())));
+        }
+        if self.match_token(&[TokenType::String]) {
+            return Ok(Expr::LiteralExpr(LiteralString(self.previous().literal)));
+        }
+        if self.match_token(&[TokenType::LeftParen]) {
+            let expr = self.expression()?;
+            self.consume(&TokenType::RightParen, String::from("Expect ')' after expression."))?;
+            return Ok(Expr::GroupingExpr(Grouping {
+                expression: Box::new(expr)
+            }));
+        } else {
+            Err(ParseError {
+                message: String::from("Unexpected token : expression expected.")
+            })
+        }
+    }
+
+    pub fn parse(&mut self) -> Option<Expr> {
+        match self.expression() {
+            Ok(expr) => Some(expr),
+            Err(error) => {
+                println!("Error while parsing expression : {}",error.message);
+                None
+            }
+        }
+    }
+}
\ No newline at end of file
diff --git a/src/rlox_interpreter.rs b/src/rlox_interpreter.rs
index 850cfcb..f4bc270 100644
--- a/src/rlox_interpreter.rs
+++ b/src/rlox_interpreter.rs
@@ -1,6 +1,9 @@
 use std::{fs, io};
 use crate::EX_OK;
 use std::io::Write;
+use crate::astprinter::ASTPrinter;
+use crate::expr::ExprVisitor;
+use crate::parser::Parser;
 
 use crate::scanner::Scanner;
 
@@ -40,15 +43,15 @@ impl RLoxInterpreter {
 
     fn run(&self, src: String) -> i32 {
         let mut scanner = Scanner::new( src );
-
         scanner.scan_tokens();
-        let mut current_line = 0;
-        for t in scanner.tokens {
-            if t.line!=current_line {
-                current_line = t.line;
-                println!("-- line {} --------------------", current_line);
-            }
-            println!("{}\t{}\t{}", t.token_type, t.lexeme, t.literal);
+
+        let mut parser = Parser::new( scanner.tokens );
+        match parser.parse() {
+            Some(expr) => {
+                let printer = ASTPrinter;
+                printer.visit_expr(&expr);
+            },
+            None => println!("An error occurred while parsing expression.")
         }
 
         EX_OK
diff --git a/src/token.rs b/src/token.rs
index deecce1..0917303 100644
--- a/src/token.rs
+++ b/src/token.rs
@@ -1,6 +1,6 @@
 use crate::token_type::TokenType;
 
-#[derive(Debug)]
+#[derive(Debug, Clone)]
 pub struct Token {
     pub token_type: TokenType,
     pub lexeme: String,