return type hint

example/hello_world.hyc

@@ -1,13 +1,15 @@
 // user defined function
-func foo :: (a, b) = {
-    return a;
+func foo :: (a, b) -> Bool = {
+    return a == b;
 };
 
 // entry point
-func main :: () = {
+func main :: () -> Int = {
     // if else in variable definition
     let cond_str :: String = if true { return "t" } else { return "f" };
 
     // Infix operator
     let n :: Bool = 2 == 2;
+    // Prefix operator
+    let m :: Bool = !n;
 };

src/front/lex.rs

@@ -32,6 +32,7 @@ syntax! { not_operator      , "!", Token::Not }
 
 // Punctuations
 syntax! { typehint_punctuation   , "::", Token::Typehint }
+syntax! { returnhint_punctuation , "->", Token::Return }
 syntax! { lparen_punctuation     , "(",  Token::LParen }
 syntax! { rparen_punctuation     , ")",  Token::RParen }
 syntax! { lbrace_punctuation     , "{",  Token::LBrace }
@@ -43,6 +44,11 @@ syntax! { comma_punctuation     , ",",  Token::Comma }
 // Operator & Punctuation
 fn lex_operator_punctuation(input: &Bytes) -> IResult<&Bytes, Token> {
     alt((
+        typehint_punctuation, returnhint_punctuation,
+        lparen_punctuation, rparen_punctuation,
+        lbrace_punctuation, rbrace_punctuation,
+        semicolon_punctuation, colon_punctuation, comma_punctuation,
+        
         equal_operator, not_equal_operator,
         less_than_operator, greater_than_operator,
         less_than_equal_operator, greater_than_equal_operator,
@@ -51,10 +57,6 @@ fn lex_operator_punctuation(input: &Bytes) -> IResult<&Bytes, Token> {
         add_operator, subtract_operator, multiply_operator, divide_operator,
         not_operator,
 
-        typehint_punctuation,
-        lparen_punctuation, rparen_punctuation,
-        lbrace_punctuation, rbrace_punctuation,
-        semicolon_punctuation, colon_punctuation, comma_punctuation,
     ))(input)
 }
 

src/front/model.rs

@@ -9,7 +9,7 @@ pub enum Token {
     Identifier(String), String(String),
     Int(i64), Bool(bool),
 
-    Assign, Typehint,
+    Assign, Typehint, Returnhint,
 
     Plus, Minus, Mul, Div, Not,
     Eq, NEq, Lt, Gt, Lte, Gte,
@@ -101,7 +101,7 @@ pub type Program = Vec<Stmt>;
 #[derive(Clone, Debug, PartialEq)]
 pub enum Stmt {
     Let(Ident, Ident, Expr),
-    Func(Ident, Vec<Ident>, Vec<Stmt>),
+    Func(Ident, Vec<Ident>, Ident, Vec<Stmt>),
     Call(Ident, Vec<Expr>),
     Return(Expr),
 }
@@ -138,6 +138,7 @@ pub struct Ident(pub String);
 
 #[derive(Clone, Debug, PartialEq)]
 pub enum Prefix {
+    Plus, Minus,
     Not,
 }
 

src/front/parser.rs

@@ -9,7 +9,7 @@ use nom::{
     sequence::{terminated, tuple, pair, preceded, delimited}, error_position,
 };
 
-use super::model::{Token, Tokens, Precedence, Infix, Program, Stmt, Expr, Ident, Literal};
+use super::model::{Token, Tokens, Precedence, Infix, Program, Stmt, Expr, Ident, Literal, Prefix};
 
 macro_rules! tag_token (
     ($func_name:ident, $tag: expr) => (
@@ -25,8 +25,13 @@ tag_token!(tag_return, Token::Return);
 tag_token!(tag_if, Token::If);
 tag_token!(tag_else, Token::Else);
 
+tag_token!(tag_plus, Token::Plus);
+tag_token!(tag_minus, Token::Minus);
+tag_token!(tag_not, Token::Not);
+
 tag_token!(tag_assign, Token::Assign);
 tag_token!(tag_typehint, Token::Typehint);
+tag_token!(tag_returnhint, Token::Return);
 tag_token!(tag_semicolon, Token::Semicolon);
 tag_token!(tag_lparen, Token::LParen);
 tag_token!(tag_rparen, Token::RParen);
@@ -73,10 +78,16 @@ fn parse_atom_expr(input: Tokens) -> IResult<Tokens, Expr> {
     alt((
         parse_literal_expr,
         parse_ident_expr,
+        parse_prefix_expr,
+        parse_paren_expr,
         parse_if_expr,
     ))(input)
 }
  
+fn parse_paren_expr(input: Tokens) -> IResult<Tokens, Expr> {
+    delimited(tag_lparen, parse_expr_lowest, tag_rparen)(input)
+}
+
 fn parse_ident(input: Tokens) -> IResult<Tokens, Ident> {
     let (i1, t1) = take(1usize)(input)?;
     if t1.tokens.is_empty() { Err(Err::Error(Error::new(input, ErrorKind::Tag))) }
@@ -128,6 +139,20 @@ fn parse_infix_expr(input: Tokens, left: Expr) -> IResult<Tokens, Expr> {
     }
 }
 
+fn parse_prefix_expr(input: Tokens) -> IResult<Tokens, Expr> {
+    let (i1, t1) = alt((tag_plus, tag_minus, tag_not))(input)?;
+    if t1.tokens.is_empty() { Err(Err::Error(error_position!(input, ErrorKind::Tag))) }
+    else {
+        let (i2, e) = parse_atom_expr(i1)?;
+        match t1.tokens[0].clone() {
+            Token::Plus => Ok((i2, Expr::Prefix(Prefix::Plus, Box::new(e)))),
+            Token::Minus => Ok((i2, Expr::Prefix(Prefix::Minus, Box::new(e)))),
+            Token::Not => Ok((i2, Expr::Prefix(Prefix::Not, Box::new(e)))),
+            _ => Err(Err::Error(error_position!(input, ErrorKind::Tag))),
+        }
+    }
+}
+
 fn parse_expr(input: Tokens, precedence: Precedence, left: Expr) -> IResult<Tokens, Expr> {
     let (i1, t1) = take(1usize)(input)?;
 
@@ -221,11 +246,13 @@ fn parse_func_stmt(input: Tokens) -> IResult<Tokens, Stmt> {
             tag_lparen,
             alt((parse_params, empty_params)),
             tag_rparen,
+            tag_returnhint,
+            parse_ident,
             tag_assign,
             parse_block_stmt,
             opt(tag_semicolon),
         )),
-        |(_, ident, _, _, params, _, _, block, _)| Stmt::Func(ident, params, block),
+        |(_, ident, _, _, params, _, _, returntype, _, block, _)| Stmt::Func(ident, params, returntype, block),
     )(input)
 }