Parser implements examples

- Function call is now stmt (muhehe)

able-script-test/melo-hello.able

@@ -1,3 +1,3 @@
 var hi = "wonk";
 melo hi;
-hi print; #Should error out
+hi print; # Should error out

src/main.rs

@@ -8,6 +8,7 @@ mod repl;
 mod variables;
 
 use clap::{App, Arg};
+use logos::Source;
 use parser::Parser;
 fn main() {
     // variables::test();
@@ -34,7 +35,17 @@ fn main() {
             // Parse
             let mut parser = Parser::new(&source);
             let ast = parser.init();
-            println!("{:#?}", ast);
+            match ast {
+                Ok(ast) => println!("{:#?}", ast),
+                Err(e) => {
+                    println!(
+                        "Error `{:?}` occured at span: {:?} = `{:?}`",
+                        e.kind,
+                        e.position.clone(),
+                        source.slice(e.position)
+                    );
+                }
+            }
         }
         None => {
             println!(

src/parser/item.rs

@@ -27,7 +27,6 @@ pub enum Expr {
     Subtract { left: Box<Expr>, right: Box<Expr> },
     Multiply { left: Box<Expr>, right: Box<Expr> },
     Divide { left: Box<Expr>, right: Box<Expr> },
-    FunctionCall { iden: Iden, args: Vec<Expr> },
     Literal(Value),
     Identifier(Iden),
 }
@@ -56,6 +55,10 @@ pub enum Stmt {
         cond: Box<Item>,
         body: Vec<Item>,
     },
-
+    FunctionCall {
+        iden: Iden,
+        args: Vec<Expr>,
+    },
+    Print(Expr),
     Melo(Iden),
 }

src/parser/mod.rs

@@ -35,9 +35,11 @@ impl<'a> Parser<'a> {
             if token.is_none() {
                 return Ok(self.ast.clone());
             };
-
-            let expr = self.parse_item(token)?;
-            self.ast.push(expr);
+            if matches!(token, Some(Token::Comment)) {
+                continue;
+            }
+            let item = self.parse_item(token)?;
+            self.ast.push(item);
         }
     }
 
@@ -112,9 +114,15 @@ impl<'a> Parser<'a> {
     fn function_declaration(&mut self) -> ParseResult {
         let iden = self.require_iden()?;
         self.require(Token::LeftParenthesis)?;
-        let args = vec![];
-        self.require(Token::RightParenthesis)?;
-
+        let mut args = vec![];
+        loop {
+            let next = self.lexer.next();
+            match next {
+                Some(Token::RightParenthesis) => break,
+                Some(Token::Identifier(i)) => args.push(Iden(i)),
+                _ => return Err(self.unexpected_token(None)),
+            }
+        }
         self.require(Token::LeftBrace)?;
         // Parse function body
         let body = self.parse_body()?;

src/parser/ops.rs

@@ -2,12 +2,17 @@ use super::*;
 
 type ExprResult = Result<Expr, Error>;
 
+/// Generate infix expression by pattern left <op> right
+///
+/// Credits: `@! ! Reiter#4543`
 #[macro_export]
 macro_rules! gen_infix {
     ($($fn_name: ident => $type: tt);*$(;)?) => {$(
+        /// Generated function for infix operator
         fn $fn_name(&mut self, left: Expr) -> ExprResult {
+            self.lexer.next();
             let next = self.lexer.next();
-            let right = self.ensure_expr(next)?;
+            let right = self.parse_expr(next)?;
             Ok(Expr::$type { left: Box::new(left), right: Box::new(right) })
         })*
     };
@@ -15,14 +20,23 @@ macro_rules! gen_infix {
 
 impl<'a> Parser<'a> {
     pub(super) fn parse_ops(&mut self, token: Token) -> ParseResult {
-        let mut buf: Expr = self.ensure_expr(Some(token))?;
+        if matches!(self.lexer.peek(), Some(Token::LeftParenthesis)) {
+            return self.fn_call(token);
+        }
+
+        let mut buf: Expr = self.parse_expr(Some(token))?;
 
         loop {
-            buf = match self.lexer.next() {
+            buf = match self.lexer.peek() {
                 Some(Token::Addition) => self.addition(buf)?,
                 Some(Token::Subtract) => self.subtract(buf)?,
                 Some(Token::Multiply) => self.multiply(buf)?,
                 Some(Token::Divide) => self.divide(buf)?,
+                Some(Token::Print) => {
+                    self.lexer.next();
+                    self.require(Token::Semicolon)?;
+                    return Ok(Stmt::Print(buf).into());
+                }
                 _ => return Ok(buf.into()),
             }
         }
@@ -37,41 +51,84 @@ impl<'a> Parser<'a> {
     }
 
     /// Ensure that input token is an expression
-    fn ensure_expr(&mut self, token: Option<Token>) -> ExprResult {
+    fn parse_expr(&mut self, token: Option<Token>) -> ExprResult {
         let token = token.ok_or(Error {
             kind: ErrorKind::EndOfTokenStream,
             position: self.lexer.span(),
         })?;
+
         match token {
             Token::Boolean(b) => Ok(Expr::Literal(Value::Bool(b))),
             Token::Integer(i) => Ok(Expr::Literal(Value::Int(i))),
             Token::String(s) => Ok(Expr::Literal(Value::Str(s))),
             Token::Aboolean(a) => Ok(Expr::Literal(Value::Abool(a))),
             Token::Identifier(i) => Ok(Expr::Identifier(Iden(i))),
+            Token::LeftParenthesis => self.parse_paren(),
             t => Err(self.unexpected_token(Some(t))),
         }
     }
 
-    /// Parse function call
-    fn fn_call(&mut self, iden: Iden) -> ExprResult {
-        return todo!();
-        self.lexer.next();
-        let mut args: Vec<Expr> = Vec::new();
-
-        while let Some(token) = self.lexer.peek() {
-            match token {
-                Token::Identifier(id) => {
-                    args.push(Expr::Identifier(Iden(id.clone())));
-                    self.lexer.next();
-                }
-                Token::RightParenthesis => break,
-                _ => {
+    /// Parse parenthesieted expression
+    fn parse_paren(&mut self) -> ExprResult {
         let next = self.lexer.next();
+        let mut buf = self.parse_expr(next)?;
+        loop {
+            let next = self.lexer.peek().clone().ok_or(Error {
+                kind: ErrorKind::EndOfTokenStream,
+                position: self.lexer.span(),
+            })?;
+
+            buf = match Some(next) {
+                Some(Token::Addition) => self.addition(buf)?,
+                Some(Token::Subtract) => self.subtract(buf)?,
+                Some(Token::Multiply) => self.multiply(buf)?,
+                Some(Token::Divide) => self.divide(buf)?,
+                Some(Token::LeftParenthesis) => {
+                    return Err(Error {
+                        kind: ErrorKind::SyntaxError(
+                            "Function call isn't an expression!".to_owned(),
+                        ),
+                        position: self.lexer.span(),
+                    })
+                }
+                Some(Token::RightParenthesis) => {
+                    self.lexer.next();
+                    return Ok(buf);
+                }
+                _ => return Ok(buf.into()),
+            };
         }
     }
-            self.require(Token::Comma)?;
+
+    /// Parse function call
+    fn fn_call(&mut self, token: Token) -> ParseResult {
+        let iden = if let Token::Identifier(i) = token {
+            Iden(i)
+        } else {
+            return Err(Error {
+                kind: ErrorKind::InvalidIdentifier,
+                position: self.lexer.span(),
+            });
+        };
+
+        self.lexer.next();
+        let mut args = Vec::new();
+        loop {
+            let next = self.lexer.next();
+
+            // No argument function
+            if matches!(next, Some(Token::RightParenthesis)) {
+                break;
             }
-        self.require(Token::RightParenthesis)?;
-        Ok(Expr::FunctionCall { iden, args })
+
+            args.push(self.parse_expr(next)?);
+            match self.lexer.next() {
+                Some(Token::RightParenthesis) => break,
+                Some(Token::Comma) => continue,
+                _ => return Err(self.unexpected_token(None)),
+            }
+        }
+        self.require(Token::Semicolon)?;
+        Ok(Stmt::FunctionCall { iden, args }.into())
     }
 }

src/repl.rs

@@ -1,3 +1,4 @@
+use logos::Source;
 use rustyline::Editor;
 
 use crate::parser::Parser;
@@ -14,7 +15,17 @@ pub fn repl() {
                 }
                 let mut parser = Parser::new(&line);
                 let ast = parser.init();
-                println!("{:#?}", ast);
+                match ast {
+                    Ok(ast) => println!("{:?}", ast),
+                    Err(e) => {
+                        println!(
+                            "Error `{:?}` occured at span: {:?} = `{:?}`",
+                            e.kind,
+                            e.position.clone(),
+                            line.slice(e.position)
+                        );
+                    }
+                }
             }
             Err(rustyline::error::ReadlineError::Eof) => {
                 println!("bye");