feat: Implement interpreter for core expressions and print statements

.kdev4/fddl.kdev4

@@ -1,5 +0,0 @@
-[Buildset]
-BuildItems=@Variant(\x00\x00\x00\t\x00\x00\x00\x00\x01\x00\x00\x00\x0b\x00\x00\x00\x00\x01\x00\x00\x00\x08\x00f\x00d\x00d\x00l)
-
-[Project]
-VersionControlSupport=kdevgit

src/interpreter/evaluator.rs

@@ -0,0 +1,195 @@
+use crate::parser::ast::{Expression, Statement, Literal, Operator};
+
+#[derive(Debug, Clone, PartialEq)]
+pub enum FddlValue {
+    Number(f64),
+    Boolean(bool),
+    String(String),
+    Nil,
+}
+
+impl std::fmt::Display for FddlValue {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            FddlValue::Number(n) => write!(f, "{}", n),
+            FddlValue::Boolean(b) => write!(f, "{}", b),
+            FddlValue::String(s) => write!(f, "{}", s),
+            FddlValue::Nil => write!(f, "nil"),
+        }
+    }
+}
+
+#[derive(Debug)]
+pub enum RuntimeError {
+    TypeMismatch(String),
+    UndefinedVariable(String),
+}
+
+pub struct Evaluator;
+
+impl Evaluator {
+    pub fn new() -> Self {
+        Evaluator
+    }
+
+    pub fn evaluate_program(&mut self, statements: Vec<Statement>) -> Result<(), RuntimeError> {
+        for statement in statements {
+            self.evaluate_statement(&statement)?;
+        }
+        Ok(())
+    }
+
+    fn evaluate_statement(&mut self, statement: &Statement) -> Result<(), RuntimeError> {
+        match statement {
+            Statement::PrintStatement(expr) => {
+                let value = self.evaluate_expression(expr)?;
+                println!("{}", value);
+            }
+
+            Statement::ExpressionStatement(expr) => {
+                self.evaluate_expression(expr)?; 
+            }
+
+            _ => {
+                println!("Interpreter: Skipping unimplemented statement: {:?}", statement);
+            }
+        }
+        Ok(())
+    }
+
+    fn evaluate_expression(&mut self, expression: &Expression) -> Result<FddlValue, RuntimeError> {
+        match expression {
+            Expression::Literal(literal) => {
+                match literal {
+                    Literal::Number(n) => Ok(FddlValue::Number(*n)),
+                    Literal::Boolean(b) => Ok(FddlValue::Boolean(*b)),
+                    Literal::String(s) => Ok(FddlValue::String(s.clone())),
+                    Literal::Nil => Ok(FddlValue::Nil),
+                }
+            }
+
+            Expression::Unary(op, right_expr) => {
+                let right_val = self.evaluate_expression(right_expr)?;
+                match op {
+                    Operator::Minus => {
+                        if let FddlValue::Number(n) = right_val {
+                            Ok(FddlValue::Number(-n))
+                        } else {
+                            Err(RuntimeError::TypeMismatch(
+                                "Operand for unary '-' must be a number.".to_string(),
+                            ))
+                        }
+                    }
+                    Operator::Not => {
+                        if let FddlValue::Boolean(b) = right_val {
+                            Ok(FddlValue::Boolean(!b))
+                        } else {
+                            Err(RuntimeError::TypeMismatch(
+                                "Operand for 'not' must be a boolean.".to_string(),
+                            ))
+                        }
+                    }
+                    Operator::Some => {
+                        Ok(right_val) 
+                    }
+                    Operator::Almost => {
+                        if let FddlValue::Number(n) = right_val {
+                            Ok(FddlValue::Number(n.round())) 
+                        } else {
+                            Err(RuntimeError::TypeMismatch(
+                                "Operand for unary '~' (Almost) must be a number for this example.".to_string(),
+                            ))
+                        }
+                    }
+                    _ => Err(RuntimeError::TypeMismatch(format!(
+                        "Unsupported unary operator {:?}.",
+                        op
+                    ))),
+                }
+            }
+
+            Expression::Binary(left_expr, op, right_expr) => { // Add this new arm
+                let left_val = self.evaluate_expression(left_expr)?;
+                let right_val = self.evaluate_expression(right_expr)?;
+
+                // Now, perform the operation based on 'op' and the types of left_val and right_val
+                match op {
+                    Operator::Plus => {
+                        // Example for addition (assuming numbers for now)
+                        if let (FddlValue::Number(l), FddlValue::Number(r)) = (&left_val, &right_val) {
+                            Ok(FddlValue::Number(l + r))
+                        } else {
+                            // Later, you might allow string concatenation here
+                            Err(RuntimeError::TypeMismatch(
+                                format!("Operands for '+' must be numbers. Got {:?} and {:?}", left_val, right_val)
+                            ))
+                        }
+                    }
+                    Operator::Minus => { // Binary Minus
+                        if let (FddlValue::Number(l), FddlValue::Number(r)) = (&left_val, &right_val) {
+                            Ok(FddlValue::Number(l - r))
+                        } else {
+                            Err(RuntimeError::TypeMismatch(
+                                format!("Operands for '-' must be numbers. Got {:?} and {:?}", left_val, right_val)
+                            ))
+                        }
+                    }
+                    Operator::Multiply => {
+                        if let (FddlValue::Number(l), FddlValue::Number(r)) = (&left_val, &right_val) {
+                            Ok(FddlValue::Number(l * r))
+                        } else {
+                            Err(RuntimeError::TypeMismatch(
+                                format!("Operands for '*' must be numbers. Got {:?} and {:?}", left_val, right_val)
+                            ))
+                        }
+                    }
+                    Operator::Divide => {
+                        if let (FddlValue::Number(l), FddlValue::Number(r)) = (&left_val, &right_val) {
+                            if *r == 0.0 {
+                                Err(RuntimeError::TypeMismatch("Division by zero.".to_string())) // Or a specific DivisionByZero error
+                            } else {
+                                Ok(FddlValue::Number(l / r))
+                            }
+                        } else {
+                            Err(RuntimeError::TypeMismatch(
+                                format!("Operands for '/' must be numbers. Got {:?} and {:?}", left_val, right_val)
+                            ))
+                        }
+                    }
+                    Operator::Modulus => { // Assuming you have Operator::Modulus from earlier
+                        if let (FddlValue::Number(l), FddlValue::Number(r)) = (&left_val, &right_val) {
+                            if *r == 0.0 {
+                                Err(RuntimeError::TypeMismatch("Modulus by zero.".to_string()))
+                            } else {
+                                Ok(FddlValue::Number(l % r))
+                            }
+                        } else {
+                            Err(RuntimeError::TypeMismatch(
+                                format!("Operands for '%' must be numbers. Got {:?} and {:?}", left_val, right_val)
+                            ))
+                        }
+                    }
+                    // TODO: Add cases for Operator::Greater, Less, EqualEqual, NotEqual, And, Or etc.
+                    // These will typically operate on numbers or booleans and produce FddlValue::Boolean.
+                    _ => Err(RuntimeError::TypeMismatch(format!(
+                        "Unsupported binary operator {:?}.",
+                        op
+                    ))),
+                }
+            }
+
+            Expression::Grouping(inner_expr) => {
+                self.evaluate_expression(inner_expr)
+            }
+
+            _ => {
+                println!("Interpreter: Unimplemented expression: {:?}", expression);
+                Err(RuntimeError::TypeMismatch(format!(
+                    "Unimplemented expression type: {:?}",
+                    expression
+                )))
+            }
+        }
+    }
+
+}

src/interpreter/mod.rs

@@ -0,0 +1 @@
+pub mod evaluator;

src/lexer/lexer.rs

@@ -269,6 +269,7 @@ impl Lexer {
             "else" => Token::Else,
             "true" => Token::True,
             "false" => Token::False,
+            "nil" => Token::Nil,
             "let" => Token::Let,
             "const" => Token::Const,
             "func" => Token::Func,

src/lexer/token.rs

@@ -35,6 +35,7 @@ pub enum Token {
     Else,
     True,
     False,
+    Nil,
     Let,
     Const,
     Func,

src/lib.rs

@@ -1,3 +1,4 @@
 pub mod lexer;
 pub mod parser;
 pub mod compiler;
+pub mod interpreter;

src/main.rs

@@ -6,9 +6,9 @@ use std::env;
 use std::fs;
 use std::io::{self, Write};
 
-// use lexer::Lexer;
 use fddl::lexer::Lexer;
 use fddl::parser::Parser;
+use fddl::interpreter::evaluator::Evaluator;
 
 fn main() {
     let args: Vec<String> = env::args().collect();
@@ -23,7 +23,8 @@ fn main() {
 
 // basic REPL
 fn run_repl() {
-    println!("fddl repl");
+    println!("FDDL REPL");
+    println!("---------");
     loop {
         print!("fddl % ");
         io::stdout().flush().unwrap();
@@ -45,45 +46,40 @@ fn run_file(path: &str) {
     run(source);
 }
 
-// runs source code
 fn run(source: String) {
-    println!("Source: {}", source.trim()); // prints source for debugging
+    println!("Source: {}", source.trim());
 
     let mut lexer = Lexer::new(source);
     let tokens = lexer.scan_tokens();
 
-    // old code begins
-    // println!("Tokens:");
-    // for token in &tokens { // Iterate by reference if you use tokens later
-    //     println!("{:?}", token);
-    // }
-    // println!("---");
-    // old code ends - delete if not needed
+    println!("Tokens: {:?}", tokens);
 
-    let mut parser = Parser::new(tokens); // Create a new parser instance
-    let ast_statements = parser.parse_program(); // NEW!
+    let mut parser = Parser::new(tokens);
     
-    println!("Parsed Statements (AST):");
+    let program_ast = parser.parse_program(); 
 
-    for stmt in ast_statements {
-        println!("{:?}", stmt);
+    if !program_ast.is_empty() { 
+        println!("Parsed Statements (AST):");
+        for stmt in &program_ast {
+            println!("{:?}", stmt);
+        }
+    } else {
+        println!("No AST generated or parsing failed.");
     }
 
-    loop {
 
-        if parser.is_at_end() { 
-            break;
-        }
-
-        match parser.parse_statement() { 
-            Some(statement) => {
-                println!("{:?}", statement); 
-            }
-            None => {
-                println!("Parser returned None, might be an error or unhandled EOF by parse_statement.");
-                break;
+    if !program_ast.is_empty() {
+        println!("Output:"); 
+        let mut evaluator = Evaluator::new();
+        match evaluator.evaluate_program(program_ast) {
+            Ok(()) => { /* Program executed successfully */ }
+            Err(e) => {
+                eprintln!("Runtime Error: {:?}", e);
             }
         }
-
+    } else {
+        println!("Skipping execution.");
     }
+
+    println!("---"); 
 }

src/parser/ast.rs

@@ -67,4 +67,8 @@ pub enum Statement {
         body: Vec<Statement>,
     },
     ReturnStatement(Option<Expression>),
+    Assignment {
+        target_name: String,
+        value: Expression,
+    },
 }

src/parser/parser.rs

@@ -17,57 +17,46 @@ impl Parser {
         }
     }
 
-    /* fn parse_for_statement(&mut self) -> Option<Statement> {
-         if !self.match_token(Token::LeftParen) {
-              eprintln!("Error: Expected '(' after 'for'.");
-              return None;
-         }
+    // fn parse_expression_statement(&mut self) -> Option<Statement> {
+    //     let expr = self.parse_expression()?;  
+    //     if self.match_token(Token::Semicolon) {
+    //         Some(Statement::ExpressionStatement(expr))
+    //     } else {
+    //         eprintln!("Error: Expected ';' after expression statement.");
+    //         None
+    //     }
+    // }
 
-         let initializer = if self.match_token(Token::Semicolon) {
-            None 
-         } else if self.match_token(Token::Let) {
-             Some(Box::new(self.parse_variable_declaration()?))
-         } else {
-            let expr_stmt = self.parse_expression_statement()?;
-            Some(Box::new(expr_stmt))
-         };
-         let condition = if self.check(&Token::Semicolon) {
-             eprintln!("Error: For loop condition is required (for now).");
-             return None;
-         } else {
-             self.parse_expression()?  
-         };
-
-         if !self.match_token(Token::Semicolon) {
-             eprintln!("Error: Expected ';' after for loop condition.");
-             return None;
-         }
-
-         let increment = if self.check(&Token::RightParen) {
-             None
-         } else {
-             Some(self.parse_expression()?)  
-         };
-
-         if !self.match_token(Token::RightParen) {
-             eprintln!("Error: Expected ')' after for loop clauses.");
-             return None;
-         }
-
-         let body = Box::new(self.parse_statement()?);
-
-         eprintln!("Warning: For statement AST structure might need review.");
-         None
-
-    } */
-
-    fn parse_expression_statement(&mut self) -> Option<Statement> {
+    fn parse_assignment_or_expression_statement(&mut self) -> Option<Statement> {
         let expr = self.parse_expression()?;
-        if self.match_token(Token::Semicolon) {
+
+        self.skip_comments(); // Skip comments before semicolon
+
+        if self.check(&Token::Equal) {
+            self.advance();
+
+            match expr {
+                Expression::Variable(target_name) => {
+                    self.skip_comments();
+                    let value_expr = self.parse_expression()?;
+
+                    self.skip_comments();
+                    if !self.match_token(Token::Semicolon) {
+                        eprintln!("Error: Expected ';' after assignment.");
+                        return None;
+                    }
+                    Some(Statement::Assignment { target_name, value: value_expr })
+                }
+                _ => {
+                    eprintln!("Error: Invalid assignment target. Must be an identifier.");
+                    return None;
+                }
+            }
+        } else if self.match_token(Token::Semicolon) {
             Some(Statement::ExpressionStatement(expr))
         } else {
-            eprintln!("Error: Expected ';' after expression statement.");
-            None
+            eprintln!("Error: Expected '=' for assignment or ';' after expression.");
+            return None;
         }
     }
 
@@ -102,6 +91,10 @@ impl Parser {
                 self.advance();   
                 Some(Expression::Literal(Literal::Boolean(false)))
             }
+            Token::Nil => {
+                self.advance();
+                Some(Expression::Literal(Literal::Nil))
+            }
             Token::Identifier(name) => {
                 self.advance();   
                 Some(Expression::Variable(name))
@@ -312,7 +305,9 @@ impl Parser {
         self.skip_comments();
         if self.is_at_end() { return None; }
         
-        if self.check(&Token::For) {
+        if self.check(&Token::Return) {
+            self.parse_return_statement()
+        } else if self.check(&Token::For) {
             self.parse_for_statement()
         } else if self.check(&Token::Func) {
             self.parse_function_declaration()
@@ -327,7 +322,7 @@ impl Parser {
         } else if self.check(&Token::While) {
             self.parse_while_statement()
         } else {
-            self.parse_expression_statement()
+            self.parse_assignment_or_expression_statement()
         }
     }
 
@@ -734,5 +729,40 @@ impl Parser {
         matches!(self.tokens[self.current], Token::EOF)
     }
 
+    //5-28/25
+    fn parse_return_statement(&mut self) -> Option<Statement> {
+        if !self.match_token(Token::Return) {
+            eprintln!("Internal parser error: Expected 'return' token.");
+            return None;
+        }
+
+        self.skip_comments(); // Skip comments before the expression
+
+        if self.check(&Token::Semicolon) {
+            self.advance();
+            return Some(Statement::ReturnStatement(None));
+        }
+
+        if self.is_at_end() {
+            eprintln!("Error: Expected expression or ';' after 'return'.");
+            return None;
+        }
+
+        match self.parse_expression() {
+            Some(expr) => {
+                self.skip_comments(); // Skip comments after the expression
+                if !self.match_token(Token::Semicolon) {
+                    eprintln!("Error: Expected ';' after return expression.");
+                    return None;
+                }
+                Some(Statement::ReturnStatement(Some(expr)))
+            }
+            None => {
+                eprintln!("Error: Invalid expression after 'return'.");
+                None
+            }
+        }
+    }
+    
 }