block + return expressions

a.hlm

@@ -1,15 +1,5 @@
-let name: str = "john";
-println("Hello, " + name + "!");
-
-let a: num = 17, b: num = 35 in
-    let c: num = a * 2 in
-        println(b + c);
-
-// func foo (a: int, b: int) {
-//     let c = a * 2;
-// 
-//     let res = b + c in
-//         return res + a;
-// }
-
-println((\x: int -> x + 1)(1));
+println({
+    println("Hello");
+    return let x: num = 17 * 2 in
+        x + 1;
+} + 34);

src/main.rs

@@ -49,6 +49,6 @@ fn main() {
             .into_iter()
             .map(|e| e.map(|c| c.to_string()))
             .chain(parse_errs.into_iter().map(|e| e.map(|t| t.to_string())))
-            .for_each(|e| println!("{}", e));
+            .for_each(|e| println!("[{:?} {:?}] {}", e.span(), e.label(), e));
     }
 }

src/read/parse.rs

@@ -20,7 +20,7 @@ pub enum Token {
     Open(Delim), Close(Delim),
     Lambda, Arrow,
 
-    Let, In, Func,
+    Let, In, Func, Return,
 }
 
 impl Display for Token {
@@ -63,9 +63,10 @@ impl Display for Token {
             Token::Lambda => write!(f, "\\"),
             Token::Arrow  => write!(f, "->"),
 
-            Token::Let  => write!(f, "let"),
-            Token::In   => write!(f, "in"),
-            Token::Func => write!(f, "func"),
+            Token::Let    => write!(f, "let"),
+            Token::In     => write!(f, "in"),
+            Token::Func   => write!(f, "func"),
+            Token::Return => write!(f, "return"),
         }
     }
 }
@@ -119,12 +120,13 @@ pub fn lexer() -> impl Parser<char, Vec<(Token, Span)>, Error = Simple<char>> {
 
     let kw = text::ident()
         .map(|s: String| match s.as_str() {
-            "true"  => Token::Bool(true),
-            "false" => Token::Bool(false),
-            "let"   => Token::Let,
-            "in"    => Token::In,
-            "func"  => Token::Func,
-            _       => Token::Sym(s),
+            "true"   => Token::Bool(true),
+            "false"  => Token::Bool(false),
+            "let"    => Token::Let,
+            "in"     => Token::In,
+            "func"   => Token::Func,
+            "return" => Token::Return,
+            _        => Token::Sym(s),
         });
 
     let token = num
@@ -298,12 +300,30 @@ pub fn expr_parser() -> impl P<Spanned<PExpr>> {
         .boxed()
         .labelled("let..in");
 
+        let block = nested_parser(
+            expr.clone()
+                .separated_by(just(Token::Semicolon))
+                .allow_trailing(),
+            Delim::Brace,
+            |_| Vec::new(),
+        )
+        .map(PExpr::Block)
+        .labelled("block");
+
+        let ret = just(Token::Return)
+        .ignore_then(expr.clone())
+        .map(Box::new)
+        .map(PExpr::Return)
+        .labelled("return");
+
         let atom = lit
         .or(sym)
         .or(vec)
         .or(paren_expr)
         .or(lam)
         .or(let_in)
+        .or(block)
+        .or(ret)
         .map_with_span(|e, s| (e, s))
         .boxed()
         .labelled("atom");

src/read/past.rs

@@ -18,7 +18,6 @@ pub enum PBinaryOp {
 #[derive(Clone, Debug)]
 pub enum PLiteral { Num(i64), Str(String), Bool(bool) }
 
-/// Enum to represent a parsed expression
 #[derive(Clone, Debug)]
 pub enum PExpr {
     Error,
@@ -39,4 +38,17 @@ pub enum PExpr {
         vars: Vec<(String, Type, Spanned<Self>)>,
         body: Box<Spanned<Self>>,
     },
+    Block(Vec<Spanned<Self>>),
+    Return(Box<Spanned<Self>>),
+}
+
+#[derive(Clone, Debug)]
+pub enum PStmt {
+    Expr(Spanned<PExpr>),
+    Let(Vec<(String, Type, Spanned<PExpr>)>),
+    Func {
+        name: String,
+        args: Vec<(String, Type)>,
+        body: Box<Spanned<PExpr>>,
+    },
 }

src/trans/ast.rs

@@ -32,8 +32,9 @@ pub enum Expr {
     Call(Box<Self>, Vec<Self>),
     Lambda {
         args: Vec<(String, Type)>,
-        body: Box<Self>,
+        body: Vec<Self>,
     },
+    Return(Box<Self>),
 }
 
 impl Display for Expr {
@@ -69,8 +70,17 @@ impl Display for Expr {
                 for (name, ty) in args {
                     write!(f, "[{} {}]", name, ty)?;
                 }
-                write!(f, " {})", body)
+                if body.len() == 1 {
+                    write!(f, " {})", body[0])
+                } else {
+                    write!(f, " (do")?;
+                    for e in body {
+                        write!(f, " {}", e)?;
+                    }
+                    write!(f, "))")
+                }
             },
+            Expr::Return(e) => write!(f, "(return {})", e),
         }
     }
 }

src/trans/js.rs

@@ -17,8 +17,9 @@ pub enum JSExpr {
     Method(Box<Self>, String, Vec<Self>),
     Lambda {
         args: Vec<(String, Type)>,
-        body: Box<Self>,
+        body: Vec<Self>,
     },
+    Return(Box<Self>),
 }
 
 impl Display for JSExpr {
@@ -74,8 +75,18 @@ impl Display for JSExpr {
                     }
                     write!(f, "{}", name)?;
                 }
-                write!(f, ") => {})", body)
+                // write!(f, ") => {})", body)
+                if body.len() == 1 {
+                    write!(f, ") => {})", body[0])
+                } else {
+                    write!(f, ") => {{")?;
+                    for e in body {
+                        write!(f, "{};", e)?;
+                    }
+                    write!(f, "}})")
+                }
             },
+            JSExpr::Return(e) => write!(f, "return {}", e),
         }
     }
 }

src/trans/low.rs

@@ -49,7 +49,7 @@ pub fn translate_expr(expr: PExpr) -> Expr {
         ),
         PExpr::Lambda { args, body } => Expr::Lambda {
             args,
-            body: Box::new(translate_expr((*body).0)),
+            body: vec![translate_expr((*body).0)],
         },
         PExpr::Let { vars, body } => {
             let mut expr: Expr = translate_expr(body.0); // The expression we're building up
@@ -58,14 +58,22 @@ pub fn translate_expr(expr: PExpr) -> Expr {
                 // Build up the lambda
                 expr = Expr::Lambda {
                     args: vec![(name, ty)],
-                    body: Box::new(expr),
+                    body: vec![expr],
                 };
                 // Call the lambda with the value
                 let val = translate_expr(val.0);
                 expr = Expr::Call(Box::new(expr), vec![val]);
             }
             expr
-        }
+        },
+        PExpr::Block(es) => {
+            let lam = Expr::Lambda {
+                args: vec![],
+                body: es.into_iter().map(|e| translate_expr(e.0)).collect(),
+            };
+            Expr::Call(Box::new(lam), vec![])
+        },
+        PExpr::Return(e) => Expr::Return(Box::new(translate_expr((*e).0))),
     }
 }
 
@@ -126,7 +134,8 @@ pub fn translate_js(expr: Expr) -> JSExpr {
         }
         Expr::Lambda { args, body } => JSExpr::Lambda {
             args,
-            body: Box::new(translate_js(*body)),
+            body: body.into_iter().map(translate_js).collect(),
         },
+        Expr::Return(e) => JSExpr::Return(Box::new(translate_js(*e))),
     }
 }