Nitpicks

This preps for Order of Operations

dee-mode.el

@@ -2,12 +2,6 @@
 
 (add-to-list 'auto-mode-alist '("\\.dee\\'" . dee-mode))
 
-(defface dee-function-param-face
-  '((t . (:slant italic
-	  :weight bold
-	  :foreground "orange")))
-  "A face to help identify function parameter in Deelang.")
-
 (defcustom dee-indent-offset 4
   "Default indentation offset for Deelang."
   :group 'dee
@@ -34,14 +28,14 @@
 (defvar dee-font-lock-keywords
   `(,(rx symbol-start
 	 (or
-	  "if" "elif" "else" "")
+	  "if" "elif" "else" "loop" "until" "over" "in" "")
 	 symbol-end)
     (,(rx (group (regexp dee-font-lock-id-re)) (* space) "<-")
      (1 font-lock-variable-name-face))
-    (,(rx (group (regexp dee-font-lock-id-re)) (* space) "->")
-     (1 'dee-function-param-face))
     (,(rx (group (regexp dee-font-lock-id-re)) (* space) "(")
-     (1 font-lock-function-name-face))))
+     (1 font-lock-function-name-face))
+    (,(rx (group (regexp dee-font-lock-id-re)) (* space) "->")
+     (1 font-lock-constant-face))))
 
 (defun dee-indent-line-function ()
   'noindent) ;TODO

demo/blockexample.dee

@@ -2,7 +2,6 @@ fun <- ->
     do-something()
     do-something-else()
 
-
 foo <- ->
     bar <- ->
         baz <- ->
@@ -11,8 +10,7 @@ foo <- ->
 
 foo() ## Inside foo but not in baz or bar
 
-add <- x -> y ->
-    return x + y ## Multivariable functions by currying
+add <- x -> y -> x + y ## Multivariable functions by currying
 
 add(x) ## Returns a _function_
 add(x, y) ## This is equivalent to add(x)(y)

demo/buildup.dee

@@ -7,7 +7,7 @@ foo <- -> bar() ## function definitions
 foo <- ->
     bar()
     baz()
-## functions with block statements
+# functions with block statements
 foo <- x -> y -> x * y + 7 ## Multiple argument functions
 if test?()
     do-something()
@@ -24,8 +24,8 @@ else
         do-a-real-bad-thing()
 ## Nested blocks
 
-obj <- {
-    field <- "hello"
-    method <- x -> x * 2
-}
-## Object creation
+i <- 1
+loop until i > 10
+     print(i)
+     i <- 1
+## Loops

demo/example.dee

@@ -1,24 +1,11 @@
-## By the end of the book I want to have an interpreter
-## for this little language, maybe a compiler too
-
 print(1 + 1) ## 2
 print("Hello world!") ## Hello world
 
-name <- read()
-print("Hi there $name") ## Hi there <name>
-
 have <- 10
 want <- 11
 need <- have - want ## This is subtraction
 have-want <- 1 ## This is a variable named "have-want"
 
-print(HaVe-WAnt) ## 1 (case doesn't matter)
-%%option meaningful-casing
-Apples <- 1
-print(apples) ## <undef> (or maybe it does)
-
-print("one fish"); print("two fish") ## Two statements on the same line
-
 say-hi <- -> print("Hi from inside a function")
 say-hi() ## Hi from inside a function
 
@@ -31,8 +18,8 @@ duck <- {
 	eats? <- food -> food = "bread"
 } ## Objects created on the fly
 
-print duck.eats?("bread") ## true
-print duck.eats?("corn") ## false
+print(duck.eats?("bread")) ## true
+print(duck.eats?("corn")) ## false
 
 cow <- {
 	talk <- print("Moo")
@@ -43,11 +30,11 @@ human <- {
 	eats? <- _ -> true
 }
 
-print cow.eats?("grass") ## true
-print cow.eats?("corn") ## true
+print(cow.eats?("grass")) ## true
+print(cow.eats?("corn")) ## true
 
 talk-or-pass-wind <- character ->
-	if character has talk then
+	if character has talk
 		character.talk()
 	else
 		print("*Fart*")

demo/real.dee

@@ -0,0 +1,18 @@
+## Obligatory
+fizzbuzz <- ->
+  loop over x in range(100)
+    if x % 15 = 0 print("fizzbuzz")
+    elif x % 3 = 0 print("fizz")
+    elif x % 5 = 0 print("buzz")
+    else print(x)
+
+fizzbuzz()
+
+print()
+
+ack <- m -> n ->
+  if m = 0 n + 1
+  elif n = 0 ack(m - 1, 1)
+  else ack(m - 1, ack(m, n - 1))
+
+print(ack(3, 4)) ## 125

peg.txt

@@ -1,49 +0,0 @@
-program		:= __* stmt*
-
-stmt		:= assignment /
-		   funcall stop /
-		   conditional / 
-		   expr stop
-		   
-expr		:= - _ expr /
- 		   expr "+" _ expr /
-		   expr "-" - expr /
-		   expr "*" _ expr /
-		   expr "/" _ expr /
-		   "(" _ expr ")" /
-		   ['"'] ((!['"'] [_] / #"\""#)*) ['"'] /
-		   funcall /
-		   fundef /
-		   boolean /
-		   id /
-		   num
-		
-boolean		:= ("true" / "false") _
-id		:= letter (letter / digit / ['?'|'.'|'-'])* _
-num		:= (digit+ "."? digit* / "." digit+) _
-
-assignment	:= id "<-" _ expr stop
-funcall		:= id "(" _ expr ** ("," _) ")" _
-funcdef		:= id? "->" _ block
-
-conditional	:= if __* elif* __* else? __*
-if		:= "if" _ expr block
-elif		:= "elif" _ expr block
-else		:= "else" _ block
-
-block		:= expr / indented_block
-indented_block	:= stop indent __* stmt+ dedent
-
-letter		:= ['A'..='Z'] / ['a'..='z']
-digit		:= ['0'..='9']
-
-stop		:= __+ / eof
-indent		:= ">>>"
-dedent		:= "<<<"
-
-_		:= ['\t'|' ']*
-__		:= comment? newline / comment &eof
-comment		:= "#" (!newline [_])* &(newline / eof)
-newline		:= "\r\n" \ "\r" \ "\n"
-
-eof		:= ![_]

src/emitter.rs

@@ -3,6 +3,10 @@ use std::collections::HashSet;
 
 use crate::parser;
 
+fn munge(s: &str) -> String {
+    s.replace("?", "p").replace("-", "_")
+}
+
 pub struct LexicalContext<'a> {
     parent: Option<&'a LexicalContext<'a>>,
     local: HashSet<String>,
@@ -17,12 +21,11 @@ impl <'a> LexicalContext<'a> {
 	    is_tail: false,
 	}
     }
-    #[allow(dead_code)]
     fn new(parent: &'a LexicalContext<'a>) -> Self {
 	LexicalContext {
 	    parent: Some(parent),
 	    local: HashSet::new(),
-	    is_tail: false,
+	    is_tail: parent.is_tail,
 	}
     }
     fn contains(&self, s: &str) -> bool {
@@ -33,32 +36,46 @@ impl <'a> LexicalContext<'a> {
     }
 }
 
-pub fn emit_all(w: &mut dyn Write, ast: &Vec<parser::Stmt>, ctx: &mut LexicalContext) -> std::io::Result<()> {
-    for stmt in ast {
+/// Embeds the pre-written js
+pub fn emit_injector(w: &mut dyn Write) -> std::io::Result<()>{
+    let bytes = include_bytes!("./js/deeinject.js");
+    write!(w, "{}", String::from_utf8_lossy(bytes))?;
+    Ok(())
+}
+
+pub fn emit_all(w: &mut dyn Write, ast: &[parser::Stmt], ctx: &mut LexicalContext) -> std::io::Result<()> {
+    let is_tail = ctx.is_tail;
+    ctx.is_tail = false;
+    if let Some((last, butlast)) = ast.split_last() {
+	for stmt in butlast {
 	    emit(w, stmt, ctx)?;
 	}
+	ctx.is_tail = is_tail;
+	emit(w, last, ctx)?;
+    }
     Ok(())
 }
 
 pub fn emit(w: &mut dyn Write, stmt: &parser::Stmt, ctx: &mut LexicalContext) -> std::io::Result<()> {
     match &stmt {
 	parser::Stmt::BareExpr(expr) => {
-	    write!(w, "console.log((")?;
+	    if ctx.is_tail {
+		write!(w, "return ")?;
+	    }
 	    emit_expr(w, expr, ctx)?;
-	    writeln!(w, "));")?;
+	    writeln!(w, ";")?;
 	}
 	parser::Stmt::Assignment(id, expr) => {
 	    if !ctx.contains(id) {
 		ctx.insert(id.clone());
 		write!(w, "let ")?;
 	    }
-	    write!(w, "{} = ", id)?;
+	    write!(w, "{} = ", munge(id))?;
 	    emit_expr(w, expr, ctx)?;
 	    writeln!(w, ";")?;
+	    if ctx.is_tail {
+		writeln!(w, "return;")?;
 	    }
-	parser::Stmt::Funcall(call) => {
-	    emit_expr(w, call, ctx)?;
-	    writeln!(w, ";")?;
 	}
 	parser::Stmt::Conditional(if_blocks, else_block) => {
 	    let mut first_block = true;
@@ -66,7 +83,7 @@ pub fn emit(w: &mut dyn Write, stmt: &parser::Stmt, ctx: &mut LexicalContext) ->
 		if first_block {
 		    write!(w, "if (")?;
 		} else {
-		    write!(w, " else if(")?;
+		    write!(w, "else if(")?;
 		}
 		first_block = false;
 		emit_expr(w, &if_block.guard, ctx)?;
@@ -82,6 +99,36 @@ pub fn emit(w: &mut dyn Write, stmt: &parser::Stmt, ctx: &mut LexicalContext) ->
 		writeln!(w, "}}")?;
 	    }
 	}
+	parser::Stmt::Loop(eloop) => {
+	    let is_tail = ctx.is_tail;
+	    ctx.is_tail = false;
+	    match &eloop {
+		parser::Loop::Over(id, expr, block) => {
+		    write!(w, "for (let {} of ", id)?;
+		    emit_expr(w, expr, ctx)?;
+		    writeln!(w, ") {{")?;
+		    let mut block_ctx = LexicalContext::new(ctx);
+		    emit_all(w, block, &mut block_ctx)?;
+		    writeln!(w, "}}")?;
+		    ctx.is_tail = is_tail;
+		}
+		parser::Loop::Until(guarded_block) => {
+		    write!(w, "while (!(")?;
+		    emit_expr(w, &guarded_block.guard, ctx)?;
+		    write!(w, ")) {{")?;
+		    let mut block_ctx = LexicalContext::new(ctx);
+		    emit_all(w, &guarded_block.block, &mut block_ctx)?;
+		    writeln!(w, "}}")?;
+		}
+		parser::Loop::Bare(block) => {
+		    write!(w, "for(;;){{")?;
+		    let mut block_ctx = LexicalContext::new(ctx);
+		    emit_all(w, block, &mut block_ctx)?;
+		    writeln!(w, "}}")?;
+		}
+	    }
+	    ctx.is_tail = is_tail;
+	}
     }
     Ok(())
 }
@@ -89,21 +136,34 @@ pub fn emit(w: &mut dyn Write, stmt: &parser::Stmt, ctx: &mut LexicalContext) ->
 pub fn emit_expr(w: &mut dyn Write, expr: &parser::Expr, ctx: &mut LexicalContext) -> std::io::Result<()> {
     match &expr {
 	parser::Expr::Id(id) => {
-	    write!(w, "{}", id)?;
+	    write!(w, "{}", munge(id))?;
 	}
 	parser::Expr::Atom(atom) => {
 	    write!(w, "{}", atom)?;
 	}
 	parser::Expr::Funcall(id, args) => {
-	    write!(w, "{}", id)?;
+	    write!(w, "{}", munge(id))?;
 	    if args.is_empty() {
 		write!(w, "()")?;
-	    }
+	    } else if ctx.contains(id) {
+		// Use deelang calling semantics
 		for arg in args {
 		    write!(w, "(")?;
 		    emit_expr(w, arg, ctx)?;
+		    write!(w, ")")?
+		}
+	    } else {
+		// Use JS calling semantics
+		write!(w, "(")?;
+		let (last, butlast) = args.split_last().unwrap();
+		for arg in butlast {
+		    emit_expr(w, arg, ctx)?;
+		    write!(w, ",")?
+		}
+		emit_expr(w, last, ctx)?;
 		write!(w, ")")?;
 	    }
+			
 	}
 	parser::Expr::Funcdef(arg, body) => {
 	    if let Some(arg) = arg {
@@ -113,15 +173,19 @@ pub fn emit_expr(w: &mut dyn Write, expr: &parser::Expr, ctx: &mut LexicalContex
 	    }
 	    let mut fun_ctx = LexicalContext::new(ctx);
 	    fun_ctx.is_tail = true;
-	    emit_all(w, body.as_ref(), &mut fun_ctx)?;
+	    emit_all(w, body, &mut fun_ctx)?;
 	    write!(w, "}}")?;
 	}
-	parser::Expr::Plus(e1, e2) => {
+	parser::Expr::BinaryOp(op, e1, e2) => {
 	    emit_expr(w, e1.as_ref(), ctx)?;
-	    write!(w, " + ")?;
+	    write!(w, " {} ", op)?;
 	    emit_expr(w, e2.as_ref(), ctx)?;
 	}
-	_ => todo!(),
+	parser::Expr::UnaryOp(op, e) => {
+	    write!(w, "{}(", op)?;
+	    emit_expr(w, e.as_ref(), ctx)?;
+	    write!(w, ")")?;
+	}
     }
     Ok(())
 }

src/evaluator.rs

@@ -1,139 +0,0 @@
-use std::ops;
-use std::collections::HashMap;
-
-use crate::parser::{self, GuardedBlock};
-use parser::Atom;
-
-pub struct Env<'a> {
-    pub parent: Option<&'a Env<'a>>,
-    pub values: HashMap<String, Atom>
-}
-
-impl<'a> Env<'a> {
-    pub fn global() -> Self {
-        Env {
-            parent: None,
-            values: HashMap::new(),
-        }
-    }
-    pub fn child(parent: &'a Env<'a>) -> Self {
-        Env {
-            parent: Some(parent),
-            values: HashMap::new(),
-        }
-    }
-    pub fn lookup(&self, id: &str) -> Atom {
-        if let Some(a) = self.values.get(id) {
-            a.clone()
-        } else if let Some(parent) = self.parent {
-            parent.lookup(id)
-        } else {
-            panic!("Variable {} not in scope.", id)
-        }
-    }
-    pub fn set(&mut self, id: String, atom: Atom) {
-        self.values.insert(id, atom);
-    }
-}
-
-pub fn eval(ast: &parser::Stmt, env: &mut Env) {
-    match &ast {
-        parser::Stmt::BareExpr(expr) =>
-            println!("{}", eval_expr(expr, env)),
-        parser::Stmt::Assignment(id, expr) =>
-            env.set(id.clone(), eval_expr(expr, env)),
-        parser::Stmt::Conditional(guarded_blocks, default_block) => {
-            let mut matched = false;
-            for GuardedBlock { guard, block } in guarded_blocks  {
-                let res = eval_expr(guard, env);
-                match res {
-                    Atom::Bool(true) => {
-                        matched = true;
-                        for stmt in block {
-			    eval(stmt, env);
-                        }
-                        break;
-                    }
-                    Atom::Bool(false) => continue,
-                    _ => panic!("Conditional expression does not evaluate to a bool"),
-                }
-            }
-            if !matched {
-                if let Some(block) = default_block {
-		    for stmt in block {
-			eval(stmt, env);
-		    }
-                }
-            }
-        }
-        _ => todo!(),
-    }
-}
-
-pub fn eval_expr(ast: &parser::Expr, env: &Env) -> Atom {
-    match ast {
-        parser::Expr::Id(a) => env.lookup(a),
-        parser::Expr::Atom(a) => a.clone(),
-        parser::Expr::UnaryMinus(a) => -eval_expr(a, env),
-        parser::Expr::Plus(a, b) => eval_expr(a, env) + eval_expr(b, env),
-        parser::Expr::Minus(a, b) => eval_expr(a, env) - eval_expr(b, env),
-        parser::Expr::Mult(a, b) => eval_expr(a, env) * eval_expr(b, env),
-        parser::Expr::Div(a, b) => eval_expr(a, env) / eval_expr(b, env),
-        _ => panic!("Couldn't evalute expression {{ {:?} }}", ast),
-    }
-}
-
-impl ops::Neg for Atom {
-    type Output = Self;
-
-    fn neg(self) -> Self {
-        match self {
-            Atom::Num(a) => Atom::Num(-a),
-            _ => panic!("Can't negate non-numeral type!"),
-        }
-    }
-}
-
-impl ops::Add for Atom {
-    type Output = Self;
-
-    fn add(self, other: Self) -> Self {
-        match (self, other) {
-            (Atom::Num(a), Atom::Num(b)) => Atom::Num(a + b),
-            _ => panic!("Can't add non-numeral types!"),
-        }
-    }
-}
-
-impl ops::Sub for Atom {
-    type Output = Self;
-
-    fn sub(self, other: Self) -> Self {
-        match (self, other) {
-            (Atom::Num(a), Atom::Num(b)) => Atom::Num(a - b),
-            _ => panic!("Can't subtract non-numeral types!"),
-        }
-    }
-}
-
-impl ops::Mul for Atom {
-    type Output = Self;
-
-    fn mul(self, other: Self) -> Self {
-        match (self, other) {
-            (Atom::Num(a), Atom::Num(b)) => Atom::Num(a * b),
-            _ => panic!("Can't multiply non-numeral types!"),
-        }
-    }
-}
-
-impl ops::Div for Atom {
-    type Output = Self;
-
-    fn div(self, other: Self) -> Self {
-        match (self, other) {
-            (Atom::Num(a), Atom::Num(b)) => Atom::Num(a / b),
-            _ => panic!("Can't divide non-numeral types!"),
-        }
-    }
-}

src/internal.rs

@@ -0,0 +1,3 @@
+//! Internal compiler steps, expansion, cps, optimization.
+
+

src/js/deeinject.js

@@ -0,0 +1,10 @@
+const print = console.log
+
+function range(x) {
+  const ret = []
+  for (let i = 0; i < x; i++) {
+    ret.push(i);
+  }
+  return ret
+}
+  

src/main.rs

@@ -1,6 +1,6 @@
 mod parser;
-mod evaluator;
 mod emitter;
+mod internal;
 
 use clap::Parser;
 
@@ -10,54 +10,34 @@ use std::fs::File;
 use std::path::PathBuf;
 
 #[derive(Parser, Debug)]
-#[clap(author, version, about = "Interpreter for Deelang")]
+#[clap(author, version, about = "Compiler for Deelang")]
 struct Cli {
-    #[clap(help="Specify a file to run")]
-    file: Option<PathBuf>,
-    #[clap(short, long, help="Only parse, do not evaluate")]
-    parse_only: bool,
-    #[clap(short, long, help="Cross-compile to ECMAScript")]
+    #[clap(help="Specify a file to compile")]
+    file: PathBuf,
+    #[clap(short, long, help="Emit a parse tree")]
+    parse: bool,
+    #[clap(short, long, help="Cross compile to ECMAScript")]
     ecmascript: bool,
-}
-
-fn repl(cli: &Cli) {
-    let mut global = evaluator::Env::global();
-    let mut toplevel = emitter::LexicalContext::toplevel();
-    let mut out = io::stdout();
-    loop {
-        let mut line = String::new();
-        io::stdin().read_line(&mut line).unwrap();
-        let tree = parser::parse_stmt(&line);
-        if cli.parse_only {
-            println!("{:#?}", tree);
-        } else if cli.ecmascript {
-	    emitter::emit(&mut out, &tree, &mut toplevel).ok();
-	} else {
-            evaluator::eval(&tree, &mut global);
-        }
-    }
-}
-
-fn script(cli: &Cli) {
-    let mut file = File::open(cli.file.as_ref().unwrap()).expect("Could not read file");
-    let mut prgm = String::new();
-    file.read_to_string(&mut prgm).unwrap();
-    let tree = parser::parse(&prgm);
-    if cli.parse_only {
-        println!("{:#?}", tree);
-    } else if cli.ecmascript {
-	let mut out = io::stdout();
-	let mut toplevel = emitter::LexicalContext::toplevel();
-	emitter::emit_all(&mut out, &tree, &mut toplevel).ok();
-    } else {
-        todo!();
-    }
+    #[clap(long, help="Run the preprocessor")]
+    preprocess: bool,
 }
 
 fn main() {
     let cli = Cli::parse();
-    match cli.file {
-        None => repl(&cli),
-        Some(_) => script(&cli),
+    let mut file = File::open(&cli.file).expect("Couldn't read file");
+    let mut prgm = String::new();
+    file.read_to_string(&mut prgm).unwrap();
+    if cli.preprocess {
+	println!("{}", parser::preprocess(&prgm));
+	return;
+    }
+    let tree = parser::parse(&prgm);
+    if cli.parse {
+        println!("{:#?}", tree);
+    } else if cli.ecmascript {
+	let mut out = io::stdout();
+	emitter::emit_injector(&mut out).ok();
+	let mut toplevel = emitter::LexicalContext::toplevel();
+	emitter::emit_all(&mut out, &tree, &mut toplevel).ok();
     }
 }

src/parser.rs

@@ -3,8 +3,8 @@ use std::fmt;
 #[derive(Debug,PartialEq,Clone)]
 pub enum Stmt {
     Assignment(String, Expr),
-    Funcall(Expr),
     Conditional(Vec<GuardedBlock>, Option<Block>),
+    Loop(Loop),
     BareExpr(Expr),
 }
 
@@ -14,11 +14,8 @@ pub enum Expr {
     Atom(Atom),
     Funcall(String, Vec<Expr>),
     Funcdef(Option<String>, Block),
-    UnaryMinus(Box<Expr>),
-    Plus(Box<Expr>, Box<Expr>),
-    Minus(Box<Expr>, Box<Expr>),
-    Mult(Box<Expr>, Box<Expr>),
-    Div(Box<Expr>, Box<Expr>),
+    UnaryOp(String, Box<Expr>),
+    BinaryOp(String, Box<Expr>, Box<Expr>),
 }
 
 pub type Block = Vec<Stmt>;
@@ -30,39 +27,41 @@ pub enum Atom {
     Bool(bool),
 }
 
-impl fmt::Display for Atom {
-    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
-        match self {
-            Atom::String(a) => write!(f, "\"{}\"", a),
-            Atom::Num(a) => write!(f, "{}", a),
-	    Atom::Bool(a) => write!(f, "{}", a),
-        }
-    }
-}
-
 #[derive(Debug,PartialEq,Clone)]
 pub struct GuardedBlock {
     pub guard: Expr,
     pub block: Block,
 }
 
+#[derive(Debug,PartialEq,Clone)]
+pub enum Loop {
+    Bare(Block),
+    Until(GuardedBlock),
+    Over(String, Expr, Block),
+}
+
 peg::parser! {
     grammar deelang_parser() for str {
         pub rule program() -> Vec<Stmt>
             = __*  s:stmt()* { s }
         pub rule stmt() -> Stmt
             = a:assignment() { a } /
-            f:funcall() stop() { Stmt::Funcall(f) } /
             c:conditional() { c } /
+	    l:_loop() { Stmt::Loop(l) } / 
             e:expr() stop() { Stmt::BareExpr(e) }
         rule expr() -> Expr = precedence! {
-            "-" _ e1:@ { Expr::UnaryMinus(Box::new(e1)) }
+	    e1:(@) "=" _ e2:@ { Expr::BinaryOp("=".to_string(), Box::new(e1), Box::new(e2))}
 	    --
-            e1:(@) "+" _ e2:@ { Expr::Plus(Box::new(e1), Box::new(e2)) }
-            e1:(@) "-" _ e2:@ { Expr::Minus(Box::new(e1), Box::new(e2)) }
+	    e1:(@) r:relop() e2:@ { Expr::BinaryOp(r, Box::new(e1), Box::new(e2)) }
 	    --
-            e1:(@) "*" _ e2:@ { Expr::Mult(Box::new(e1), Box::new(e2)) }
-            e1:(@) "/" _ e2:@ { Expr::Div(Box::new(e1), Box::new(e2)) }
+            "-" _ e1:@ { Expr::UnaryOp("-".to_string(), Box::new(e1)) }
+            --
+            e1:(@) "+" _ e2:@ { Expr::BinaryOp("+".to_string(), Box::new(e1), Box::new(e2)) }
+            e1:(@) "-" _ e2:@ { Expr::BinaryOp("-".to_string(), Box::new(e1), Box::new(e2)) }
+            --
+            e1:(@) "*" _ e2:@ { Expr::BinaryOp("*".to_string(), Box::new(e1), Box::new(e2)) }
+            e1:(@) "/" _ e2:@ { Expr::BinaryOp("/".to_string(), Box::new(e1), Box::new(e2)) }
+	    e1:(@) "%" _ e2:@ { Expr::BinaryOp("%".to_string(), Box::new(e1), Box::new(e2)) }
             --
             "(" _ e:expr() ")" _ { e }
             ['"'] s:$((!['"'] [_] / r#"\""#)*) ['"'] { Expr::Atom(Atom::String(s.to_string())) }
@@ -80,14 +79,16 @@ peg::parser! {
             = i:$(letter() (letter() / digit() / ['?'|'.'|'-'])*) _ { i.to_string() }
         rule assignment() -> Stmt
             = i:id() "<-" _ e:expr() stop() { Stmt::Assignment(i, e) }
+	rule relop() -> String
+	    = r:$("<" / ">" / "<=" / ">=") _ { r.to_string() } 
         rule num() -> f64
             = n:$(digit()+ "."? digit()* / "." digit()+) _ { n.parse().unwrap() }
         rule funcall() -> Expr
-            = i:id() "(" _ e:(expr() ** ("," _)) ")" _ { Expr::Funcall(i, e) }
+            = i:id() "(" _ e:(expr() ** ("," _)) __* ")" _ { Expr::Funcall(i, e) }
         rule funcdef() -> Expr
             = i:id()? "->" _ b:(block()) { Expr::Funcdef(i, b) }
         rule conditional() -> Stmt
-            = i:_if() __* ei:elif()* __* e:_else()? __* { Stmt::Conditional([vec![i], ei].concat(), e) }
+            = i:_if() __* ei:elif()* e:_else()? __* { Stmt::Conditional([vec![i], ei].concat(), e) }
         rule _if() -> GuardedBlock
             = "if" _ g:expr() b:block() {
                 GuardedBlock {
@@ -96,7 +97,7 @@ peg::parser! {
                 }
             }
         rule elif() -> GuardedBlock
-            = "elif" _ g:expr() b:block() {
+            = "elif" _ g:expr() b:block() __* {
                 GuardedBlock {
                     guard: g,
                     block: b
@@ -104,6 +105,17 @@ peg::parser! {
             }
         rule _else() -> Block
             = "else" _ b:block() { b }
+	rule _loop() -> Loop
+	    = "loop" _ "until" _ e:expr() b:block() __* {
+		Loop::Until(GuardedBlock{
+		    guard:e,
+		    block: b,
+		})
+	    } /
+	    "loop" _ "over" _ i:id() "in" _ e:expr() b:block() __* {
+		Loop::Over(i, e, b)
+	    } /
+	    "loop" _ b:block() __* { Loop::Bare(b) }
         rule block() -> Block
             = i:indented_block() { i } /
 	    e:expr() { vec![Stmt::BareExpr(e)] }
@@ -133,7 +145,7 @@ peg::parser! {
     }
 }
 
-fn preprocess(input: &str) -> String {
+pub fn preprocess(input: &str) -> String {
     let mut stack = vec![0];
     let mut output = String::new();
     for line in input.lines() {
@@ -166,6 +178,12 @@ fn preprocess(input: &str) -> String {
         output.push_str(line.trim());
         output.push('\n');
     }
+    while stack.len() > 1 {
+	// place any dedents needed to balance the program
+	output.push_str("<<<");
+        output.push('\n');
+        stack.pop();
+    }
     output
 }
 
@@ -174,9 +192,77 @@ pub fn parse(prgm: &str) -> Vec<Stmt> {
     deelang_parser::program(&prgm).unwrap()
 }
 
-pub fn parse_stmt(stmt: &str) -> Stmt {
-    let stmt = preprocess(stmt);
-    deelang_parser::stmt(&stmt).unwrap()
+impl fmt::Display for Stmt {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+	match self {
+	    Stmt::Assignment(id, expr) => writeln!(f, "{} <- {}", id, expr),
+	    Stmt::BareExpr(expr) => writeln!(f, "{}", expr),
+	    Stmt::Conditional(guarded_blocks, else_block) => {
+		let (if_block, elif_blocks) = guarded_blocks.split_first().unwrap();
+		write!(f, "if {}", if_block.guard)?;
+		write_block(f, &if_block.block)?;
+		for elif_block in elif_blocks {
+		    write!(f, "elif {}", elif_block.guard)?;
+		    write_block(f, &if_block.block)?;
+		}
+		if let Some(block) = else_block {
+		    write!(f, "else")?;
+		    write_block(f, block)?;
+		}
+		Ok(())
+	    }
+	    Stmt::Loop(loop_inner) => match &loop_inner {
+		Loop::Bare(block) => {
+		    write!(f, "loop")?;
+		    write_block(f, block)
+		}
+		Loop::Over(id, pred, block) => {
+		    write!(f, "loop over {} in {}", id, pred)?;
+		    write_block(f, block)
+		}
+		Loop::Until(guarded_block) => {
+		    write!(f, "loop until {}", guarded_block.guard)?;
+		    write_block(f, &guarded_block.block)
+		}
+	    },
+	}
+    }
+}
+
+fn write_block (f: &mut fmt::Formatter<'_>, block: &Block) -> fmt::Result {
+    if block.len() == 1 {
+	writeln!(f, " {}", block[0])
+    } else {
+	writeln!(f)?;
+	writeln!(f, ">>>")?;
+	for stmt in block {
+	    write!(f, "{}", stmt)?;
+	}
+	writeln!(f, "<<<")
+    }
+}
+
+impl fmt::Display for Expr {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+	match self {
+	    Expr::Atom(a) => write!(f, "{}", a),
+	    Expr::Id(id) => write!(f, "{}", id),
+	    Expr::BinaryOp(op, e1, e2) => write!(f, "{} {} {}", e1, op, e2),
+	    Expr::UnaryOp(op, e) => write!(f, "{} {}", op, e),
+	    Expr::Funcdef(_arg, _block) => todo!(),
+	    Expr::Funcall(_id, _args) => todo!(),
+	}
+    }
+}
+
+impl fmt::Display for Atom {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Atom::String(a) => write!(f, "\"{}\"", a),
+            Atom::Num(a) => write!(f, "{}", a),
+	    Atom::Bool(a) => write!(f, "{}", a),
+        }
+    }
 }
 
 
@@ -196,8 +282,8 @@ apple <- 1 ## This is too
     #[test]
     fn test_funcall() {
         let expected = vec![
-            Stmt::Funcall(Expr::Funcall("pear".to_string(), vec![])),
-            Stmt::Funcall(Expr::Funcall("pear".to_string(),
+            Stmt::BareExpr(Expr::Funcall("pear".to_string(), vec![])),
+            Stmt::BareExpr(Expr::Funcall("pear".to_string(),
                                         vec![Expr::Id("x".to_string()), Expr::Id("y".to_string())],
             ))
         ];
@@ -230,18 +316,22 @@ one <- 3 - 2
 four <- (3 - 1) * 2";
         let expected = vec![
             Stmt::Assignment("three".to_string(),
-                             Expr::Plus(
+                             Expr::BinaryOp(
+				 "+".to_string(),
                                  Box::new(Expr::Atom(Atom::Num(1.0))),
                                  Box::new(Expr::Atom(Atom::Num(2.0))),
                              )),
             Stmt::Assignment("one".to_string(),
-                             Expr::Minus(
+                             Expr::BinaryOp(
+				 "-".to_string(),
                                  Box::new(Expr::Atom(Atom::Num(3.0))),
                                  Box::new(Expr::Atom(Atom::Num(2.0))),
                              )),
             Stmt::Assignment("four".to_string(),
-                             Expr::Mult(
-                                 Box::new(Expr::Minus(
+                             Expr::BinaryOp(
+				 "*".to_string(),
+                                 Box::new(Expr::BinaryOp(
+				     "-".to_string(),
                                      Box::new(Expr::Atom(Atom::Num(3.0))),
                                      Box::new(Expr::Atom(Atom::Num(1.0))),
                                  )),
@@ -256,7 +346,8 @@ four <- (3 - 1) * 2";
         let prgm = "apple <- pear(x, y) + z";
         let expected = vec![
             Stmt::Assignment("apple".to_string(),
-                             Expr::Plus(
+                             Expr::BinaryOp(
+				 "+".to_string(),
                                  Box::new(Expr::Funcall(
                                      "pear".to_string(),
                                      vec![Expr::Id("x".to_string()), Expr::Id("y".to_string())],
@@ -290,8 +381,8 @@ foo <- x -> y -> x * y";
                 Expr::Funcdef(
                     None,
 		    vec![
-                        Stmt::Funcall(Expr::Funcall("bar".to_string(), vec![])),
-                        Stmt::Funcall(Expr::Funcall("baz".to_string(), vec![])),
+                        Stmt::BareExpr(Expr::Funcall("bar".to_string(), vec![])),
+                        Stmt::BareExpr(Expr::Funcall("baz".to_string(), vec![])),
                     ],
 		)
             ),
@@ -303,7 +394,8 @@ foo <- x -> y -> x * y";
                         Stmt::BareExpr(Expr::Funcdef(
                             Some("y".to_string()),
 			    vec![
-                                Stmt::BareExpr(Expr::Mult(
+                                Stmt::BareExpr(Expr::BinaryOp(
+				    "*".to_string(),
                                     Box::new(Expr::Id("x".to_string())),
                                     Box::new(Expr::Id("y".to_string())),
                                 ))
@@ -330,18 +422,30 @@ else
             vec![
                 GuardedBlock {
                     guard: Expr::Id("foo".to_string()),
-                    block: vec![Stmt::Funcall(Expr::Funcall("bar".to_string(), vec![]))]
+                    block: vec![Stmt::BareExpr(Expr::Funcall("bar".to_string(), vec![]))]
                 },
                 GuardedBlock {
                     guard: Expr::Id("baz".to_string()),
-                    block: vec![Stmt::Funcall(Expr::Funcall("foobar".to_string(), vec![]))],
+                    block: vec![Stmt::BareExpr(Expr::Funcall("foobar".to_string(), vec![]))],
                 },
             ],
-            Some(vec![Stmt::Funcall(Expr::Funcall("quux".to_string(), vec![]))]),
+            Some(vec![Stmt::BareExpr(Expr::Funcall("quux".to_string(), vec![]))]),
         )];
         assert_eq!(deelang_parser::program(prgm).unwrap(), expected);
     }
-
+    #[test]
+    fn test_loop() {
+	let prgm = r"loop until i > 100 a";
+	let expected = vec![Stmt::Loop(Loop::Until(GuardedBlock {
+	    guard: Expr::BinaryOp(
+		">".to_string(),
+		Box::new(Expr::Id("i".to_string())),
+		Box::new(Expr::Atom(Atom::Num(100.0))),
+	    ),
+	    block: vec![Stmt::BareExpr(Expr::Id("a".to_string()))],
+	}))];
+	assert_eq!(deelang_parser::program(prgm).unwrap(), expected);
+    }
     #[test]
     fn test_preprocess() {
         let prgm = r"