Implement debug print

src/interpreter.rs

@@ -22,8 +22,11 @@ impl Interpreter {
         for stmt in prog.prog {
             match stmt {
                 Stmt::Expr(expr) => {
+                    self.resolve_expr(expr);
+                }
+                Stmt::DbgPrint(expr) => {
                     let result = self.resolve_expr(expr);
-                    println!("Result = {:?}", result);
+                    println!("{:?}", result);
                 }
                 Stmt::Let(name, rhs) => {
                     let result = self.resolve_expr(rhs);

src/lexer.rs

@@ -22,6 +22,9 @@ pub enum Token {
     /// Identifier (variable / function / ... name)
     Ident(String),
 
+    /// Dollar sign ($)
+    Dollar,
+
     /// Let identifier (let)
     Let,
 
@@ -175,6 +178,7 @@ impl<'a> Lexer<'a> {
                 ';' => tokens.push(Token::Semicolon),
                 '{' => tokens.push(Token::LBrace),
                 '}' => tokens.push(Token::RBrace),
+                '$' => tokens.push(Token::Dollar),
 
                 'a'..='z' | 'A'..='Z' | '_' => {
                     let mut ident = String::from(ch);

src/parser.rs

@@ -75,6 +75,7 @@ pub enum Stmt {
     Let(String, Expr),
     While(Expr, Ast),
     If(Expr, Ast, Ast),
+    DbgPrint(Expr),
 }
 
 #[derive(Debug, PartialEq, Eq, Clone)]
@@ -108,7 +109,8 @@ stmt_expr = expr
 stmt_let = "let" IDENT "=" expr
 stmt_while = "while" expr "{" (stmt)* "}"
 stmt_if = "if" expr "{" (stmt)* "}" ( "else" "{" (stmt)* "}" )
-stmt = stmt_expr | stmt_let | stmt_while | stmt_if
+stmt_dbgprint = "$" expr
+stmt = stmt_expr | stmt_let | stmt_while | stmt_if | stmt_dbgprint
 */
 
 struct Parser<T: Iterator<Item = Token>> {
@@ -136,6 +138,10 @@ impl<T: Iterator<Item = Token>> Parser<T> {
                 Token::Let => self.parse_let_stmt(),
                 Token::While => self.parse_while(),
                 Token::If => self.parse_if(),
+                Token::Dollar => {
+                    self.next();
+                    Stmt::DbgPrint(self.parse_expr())
+                }
                 // By default try to parse an expression
                 _ => Stmt::Expr(self.parse_expr()),
             };