From 8908630a21300f8fb1daafdb135ecfae1d7ab43d Mon Sep 17 00:00:00 2001
From: Scott Richmond <kredati@users.noreply.github.com>
Date: Fri, 27 Dec 2024 00:22:01 -0500
Subject: [PATCH] add match_depth to vm

---
 src/compiler.rs | 43 ++++++++++++++++++++++++++++++++++++++++---
 src/main.rs     |  5 ++---
 src/vm.rs       | 16 +++++++++++-----
 3 files changed, 53 insertions(+), 11 deletions(-)

diff --git a/src/compiler.rs b/src/compiler.rs
index 40f56b5..64425df 100644
--- a/src/compiler.rs
+++ b/src/compiler.rs
@@ -141,6 +141,7 @@ pub struct Compiler {
     pub span: SimpleSpan,
     pub src: &'static str,
     pub name: &'static str,
+    loop_idxes: Vec<usize>,
 }
 
 fn is_binding(expr: &Spanned<Ast>) -> bool {
@@ -172,6 +173,7 @@ impl Compiler {
             nodes: vec![],
             ast: &ast.0,
             span: ast.1,
+            loop_idxes: vec![],
             src,
             name,
         }
@@ -253,6 +255,18 @@ impl Compiler {
         });
     }
 
+    fn enter_loop(&mut self) {
+        self.loop_idxes.push(self.len());
+    }
+
+    fn leave_loop(&mut self) {
+        self.loop_idxes.pop();
+    }
+
+    fn loop_idx(&mut self) -> usize {
+        *self.loop_idxes.last().unwrap()
+    }
+
     pub fn compile(&mut self) {
         use Ast::*;
         match self.ast {
@@ -472,7 +486,6 @@ impl Compiler {
                 self.visit(scrutinee.as_ref());
                 let mut jump_idxes = vec![];
                 let mut clauses = clauses.iter();
-                // TODO: add guard checking
                 while let Some((MatchClause(pattern, guard, body), _)) = clauses.next() {
                     self.scope_depth += 1;
                     self.visit(pattern);
@@ -592,14 +605,38 @@ impl Compiler {
                 // and emit nil
                 self.emit_constant(Value::Nil);
             }
+            Loop(value, clauses) => {
+                //algo:
+                //first, put the values on the stack
+                let (Ast::Tuple(members), _) = value.as_ref() else {
+                    unreachable!()
+                };
+                for member in members {
+                    self.visit(member);
+                }
+                let arity = members.len();
+                //then, save the beginning of the loop
+                self.enter_loop();
+                self.emit_op(Op::ResetMatch);
+                //next, compile each clause:
+                let mut clauses = clauses.iter();
+                while let Some((Ast::MatchClause(pattern, _, body), _)) = clauses.next() {
+                    self.scope_depth += 1;
+                    let (Ast::TuplePattern(members), _) = pattern.as_ref() else {
+                        unreachable!()
+                    };
+                }
+                //match against the values on the stack
+                //we know the (fixed) arity, so we should know where to look
+                //compile the clauses exactly as in `match`
+            }
+            Recur(args) => {}
             Interpolated(..)
             | Arguments(..)
             | Placeholder
             | Panic(..)
             | Do(..)
             | Splat(..)
-            | Loop(..)
-            | Recur(..)
             | InterpolatedPattern(..)
             | AsPattern(..)
             | Splattern(..)
diff --git a/src/main.rs b/src/main.rs
index ee5ddf1..b539c79 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -69,9 +69,8 @@ pub fn run(src: &'static str) {
 pub fn main() {
     let src = "
 match :foo with {
-    :foo if nil -> :oops
-    :foo if true -> :yay!
-    :bar -> :thing
+    :bar -> :no
+    :foo -> :yes
 }
     ";
     run(src);
diff --git a/src/vm.rs b/src/vm.rs
index 16b4843..c201906 100644
--- a/src/vm.rs
+++ b/src/vm.rs
@@ -36,6 +36,7 @@ pub struct Vm<'a> {
     pub ip: usize,
     pub return_register: Value,
     pub matches: bool,
+    pub match_depth: u8,
 }
 
 impl<'a> Vm<'a> {
@@ -46,6 +47,7 @@ impl<'a> Vm<'a> {
             ip: 0,
             return_register: Value::Nil,
             matches: false,
+            match_depth: 0,
         }
     }
 
@@ -174,6 +176,7 @@ impl<'a> Vm<'a> {
             }
             ResetMatch => {
                 self.matches = false;
+                self.match_depth = 0;
                 self.ip += 1;
                 self.interpret()
             }
@@ -183,21 +186,24 @@ impl<'a> Vm<'a> {
                 self.interpret()
             }
             MatchNil => {
-                if *self.stack.last().unwrap() == Value::Nil {
+                let idx = self.stack.len() - self.match_depth as usize - 1;
+                if self.stack[idx] == Value::Nil {
                     self.matches = true;
                 };
                 self.ip += 1;
                 self.interpret()
             }
             MatchTrue => {
-                if *self.stack.last().unwrap() == Value::True {
+                let idx = self.stack.len() - self.match_depth as usize - 1;
+                if self.stack[idx] == Value::True {
                     self.matches = true;
                 };
                 self.ip += 1;
                 self.interpret()
             }
             MatchFalse => {
-                if *self.stack.last().unwrap() == Value::False {
+                let idx = self.stack.len() - self.match_depth as usize - 1;
+                if self.stack[idx] == Value::False {
                     self.matches = true;
                 }
                 self.ip += 1;
@@ -213,8 +219,8 @@ impl<'a> Vm<'a> {
             }
             MatchConstant => {
                 let const_idx = self.chunk.bytecode[self.ip + 1];
-                let value = self.stack.last().unwrap();
-                self.matches = *value == self.chunk.constants[const_idx as usize];
+                let idx = self.stack.len() - self.match_depth as usize - 1;
+                self.matches = self.stack[idx] == self.chunk.constants[const_idx as usize];
                 self.ip += 2;
                 self.interpret()
             }