infix expr

example/hello_world.hyc

@@ -1,10 +1,13 @@
-func join :: (a, b) = {
-    let result :: String = from(a, b);
-    return result
+// user defined function
+func foo :: (a, b) = {
+    return a;
 };
 
+// entry point
 func main :: () = {
-    let foo :: String = join("f", "oo");
-    print(foo);
-    return 0
+    // if else in variable definition
+    let cond_str :: String = if true { return "t" } else { return "f" };
+
+    // Infix operator
+    let n :: Bool = 2 == 2;
 };

src/front/lex.rs

@@ -1,6 +1,6 @@
 use nom::{
     branch::alt,
-    bytes::complete::{tag, take},
+    bytes::complete::{tag, take, take_until},
     character::complete::{multispace0, alphanumeric1, alpha1, digit1},
     combinator::{map, map_res, recognize},
     IResult,
@@ -119,15 +119,27 @@ fn lex_illegal(input: &Bytes) -> IResult<&Bytes, Token> {
     map(take(1usize), |_| Token::Illegal)(input)
 }
 
+fn lex_comment(input: &Bytes) -> IResult<&Bytes, ()> {
+    let (i1, c1) = take(2usize)(input)?;
+    if c1.as_bytes() == b"//" {
+        let (i2, _) = take_until("\n")(i1)?;
+        let (i3, _) = take(1usize)(i2)?;
+        let (i4, _) = multispace0(i3)?;
+        let (i5, _) = lex_comment(i4)?;
+        Ok((i5, ()))
+    } else { Ok((input, ())) }
+}
+
 // Tokens
 fn lex_token(input: &Bytes) -> IResult<&Bytes, Token> {
+    let (i1, _) = lex_comment(input)?;
     alt((
         lex_operator_punctuation,
-        lex_string,
         lex_reserved_identifier,
+        lex_string,
         lex_integer,
         lex_illegal,
-    ))(input)
+    ))(i1)
 }
 
 fn lex_tokens(input: &Bytes) -> IResult<&Bytes, Vec<Token>> {

src/front/parser.rs

@@ -6,7 +6,7 @@ use nom::{
     error::{Error, ErrorKind},
     IResult,
     multi::many0,
-    sequence::{terminated, tuple, pair, preceded, delimited},
+    sequence::{terminated, tuple, pair, preceded, delimited}, error_position,
 };
 
 use super::model::{Token, Tokens, Precedence, Infix, Program, Stmt, Expr, Ident, Literal};
@@ -22,6 +22,8 @@ macro_rules! tag_token (
 tag_token!(tag_let, Token::Let);
 tag_token!(tag_func, Token::Func);
 tag_token!(tag_return, Token::Return);
+tag_token!(tag_if, Token::If);
+tag_token!(tag_else, Token::Else);
 
 tag_token!(tag_assign, Token::Assign);
 tag_token!(tag_typehint, Token::Typehint);
@@ -71,6 +73,7 @@ fn parse_atom_expr(input: Tokens) -> IResult<Tokens, Expr> {
     alt((
         parse_literal_expr,
         parse_ident_expr,
+        parse_if_expr,
     ))(input)
 }
  
@@ -109,6 +112,22 @@ fn parse_call_expr(input: Tokens, func_handle: Expr) -> IResult<Tokens, Expr> {
     )(input)
 }
 
+fn parse_infix_expr(input: Tokens, left: Expr) -> IResult<Tokens, Expr> {
+    let (i1, t1) = take(1usize)(input)?;
+    if t1.tokens.is_empty() { Err(Err::Error(error_position!(input, ErrorKind::Tag))) }
+    else {
+        let next = &t1.tokens[0];
+        let (prec, op) = infix_operator(next);
+        match op {
+            None => Err(Err::Error(error_position!(input, ErrorKind::Tag))),
+            Some(op) => {
+                let (i2, right) = parse_expr_with(i1, prec)?;
+                Ok((i2, Expr::Infix(op, Box::new(left), Box::new(right))))
+            } 
+        }
+    }
+}
+
 fn parse_expr(input: Tokens, precedence: Precedence, left: Expr) -> IResult<Tokens, Expr> {
     let (i1, t1) = take(1usize)(input)?;
 
@@ -121,15 +140,30 @@ fn parse_expr(input: Tokens, precedence: Precedence, left: Expr) -> IResult<Toke
                 parse_expr(i2, precedence, left2)
             },
             (ref peek, _) if precedence < *peek => {
-                // let (i2, left2) = parse_infix_expr(input, left)?;
-                // parse_expr(i2, precedence, left2)
-                todo!()
+                let (i2, left2) = parse_infix_expr(input, left)?;
+                parse_expr(i2, precedence, left2)
             },
             _ => Ok((input, left)),
         }
     }
 }
 
+fn parse_if_expr(input: Tokens) -> IResult<Tokens, Expr> {
+    map(
+        tuple((
+            tag_if,
+            parse_expr_lowest,
+            parse_block_stmt,
+            parse_else_expr,
+        )),
+        |(_, cond, then, else_)| Expr::If { cond: Box::new(cond), then, else_ },
+    )(input)
+}
+
+fn parse_else_expr(input: Tokens) -> IResult<Tokens, Option<Program>> {
+    opt(preceded(tag_else, parse_block_stmt))(input)
+}
+
 fn parse_comma_exprs(input: Tokens) -> IResult<Tokens, Expr> {
     preceded(tag_comma, parse_expr_lowest)(input)
 }