From 8e19b7c39d9b486f22870b9c66f398431ffd1c24 Mon Sep 17 00:00:00 2001
From: Greg Shuflin <greg.shuflin@protonmail.com>
Date: Wed, 3 Nov 2021 23:57:22 -0700
Subject: [PATCH] Precedence

---
 schala-lang/language/src/ast/operators.rs |  4 ++
 schala-lang/language/src/parsing/new.rs   | 47 ++++++++++++++++++++++-
 schala-lang/language/src/parsing/test.rs  | 16 ++++----
 3 files changed, 58 insertions(+), 9 deletions(-)

diff --git a/schala-lang/language/src/ast/operators.rs b/schala-lang/language/src/ast/operators.rs
index c7cbf9d..1bdc015 100644
--- a/schala-lang/language/src/ast/operators.rs
+++ b/schala-lang/language/src/ast/operators.rs
@@ -47,6 +47,10 @@ impl BinOp {
         let s = token_kind_to_sigil(op_tok)?;
         Some(binop_precedences(s))
     }
+
+    pub fn get_precedence(&self) -> i32 {
+        binop_precedences(self.sigil.as_ref())
+    }
 }
 
 fn token_kind_to_sigil(tok: &TokenKind) -> Option<&str> {
diff --git a/schala-lang/language/src/parsing/new.rs b/schala-lang/language/src/parsing/new.rs
index 181d1a3..a2b7c38 100644
--- a/schala-lang/language/src/parsing/new.rs
+++ b/schala-lang/language/src/parsing/new.rs
@@ -1,9 +1,45 @@
 use crate::ast::*;
 use std::rc::Rc;
 
+#[derive(Debug)]
+struct BinopSequence {
+    first: ExpressionKind,
+    next: Vec<(BinOp, ExpressionKind)>,
+}
+
+impl BinopSequence {
+    fn do_precedence(self) -> ExpressionKind {
+        fn helper(precedence: i32, lhs: ExpressionKind, rest: &mut Vec<(BinOp, ExpressionKind)>) -> Expression {
+            let mut lhs = Expression::new(Default::default(), lhs);
+            loop {
+                let (next_op, next_rhs) = match rest.pop() {
+                    Some((a, b)) => (a, b),
+                    None => break,
+                };
+                let new_precedence = next_op.get_precedence();
+                if precedence >= new_precedence {
+                    rest.push((next_op, next_rhs));
+                    break;
+                }
+                let rhs = helper(new_precedence, next_rhs, rest);
+                lhs = Expression::new(Default::default(),
+                    ExpressionKind::BinExp(next_op, Box::new(lhs), Box::new(rhs))
+                );
+            }
+            lhs
+        }
+        let mut as_stack = self.next.into_iter().rev().collect();
+        helper(BinOp::min_precedence(), self.first, &mut as_stack).kind
+    }
+}
+
 peg::parser! {
     pub grammar schala_parser() for str {
 
+        rule whitespace() = [' ' | '\t']*
+
+        rule _ = quiet!{ whitespace() }
+
         pub rule program() -> AST =
             n:(statement() ** delimiter() ) { AST { id: Default::default(), statements: n.into() } }
 
@@ -18,7 +54,16 @@ peg::parser! {
             kind:expression_kind() { Expression { id: Default::default(), type_anno: None, kind: kind } }
 
         rule expression_kind() -> ExpressionKind =
-            primary()
+            precedence_expr()
+
+        rule precedence_expr() -> ExpressionKind =
+            first:primary() _ next:(precedence_continuation())* {
+                let next = next.into_iter().map(|(sigil, expr)| (BinOp::from_sigil(sigil), expr)).collect();
+                BinopSequence { first, next }.do_precedence()
+            }
+
+        rule precedence_continuation() -> (&'input str, ExpressionKind) =
+            op:operator() _ expr:primary() _ { (op, expr) }
 
         //TODO maybe make this more complex
         rule operator() -> &'input str =
diff --git a/schala-lang/language/src/parsing/test.rs b/schala-lang/language/src/parsing/test.rs
index f0f2bc3..6d569c9 100644
--- a/schala-lang/language/src/parsing/test.rs
+++ b/schala-lang/language/src/parsing/test.rs
@@ -172,7 +172,7 @@ fn binexps() {
     use ExpressionKind::*;
     use StatementKind::Expression;
 
-    assert_expr!("0xf_f_+1", binop("+", expr(NatLiteral(255)), expr(NatLiteral(1))));
+    assert_expr2!("0xf_f_+1", binop("+", expr(NatLiteral(255)), expr(NatLiteral(1))));
     assert_eq!(
         parse("3; 4; 4.3").unwrap(),
         AST {
@@ -186,16 +186,16 @@ fn binexps() {
         }
     );
 
-    assert_expr!(
+    assert_expr2!(
         "1 + 2 * 3",
         binop("+", expr(NatLiteral(1)), binop("*", expr(NatLiteral(2)), expr(NatLiteral(3))))
     );
-    assert_expr!(
+    assert_expr2!(
         "1 * 2 + 3",
         binop("+", binop("*", expr(NatLiteral(1)), expr(NatLiteral(2))), expr(NatLiteral(3)))
     );
-    assert_expr!("1 && 2", binop("&&", expr(NatLiteral(1)), expr(NatLiteral(2))));
-    assert_expr!(
+    assert_expr2!("1 && 2", binop("&&", expr(NatLiteral(1)), expr(NatLiteral(2))));
+    assert_expr2!(
         "1 + 2 * 3 + 4",
         binop(
             "+",
@@ -203,12 +203,12 @@ fn binexps() {
             expr(NatLiteral(4))
         )
     );
-    assert_expr!(
+    assert_expr2!(
         "(1 + 2) * 3",
         binop("*", binop("+", expr(NatLiteral(1)), expr(NatLiteral(2))), expr(NatLiteral(3)))
     );
-    assert_expr!(".1 + .2", binop("+", expr(FloatLiteral(0.1)), expr(FloatLiteral(0.2))));
-    assert_expr!("1 / 2.", binop("/", expr(NatLiteral(1)), expr(FloatLiteral(2.))));
+    assert_expr2!(".1 + .2", binop("+", expr(FloatLiteral(0.1)), expr(FloatLiteral(0.2))));
+    assert_expr2!("1 / 2.", binop("/", expr(NatLiteral(1)), expr(FloatLiteral(2.))));
 }
 
 #[test]