From e4b385d2fb03b25e84ae1457775bd3c6777a6006 Mon Sep 17 00:00:00 2001
From: Scott Richmond <kredati@users.noreply.github.com>
Date: Mon, 23 Jun 2025 00:27:50 -0400
Subject: [PATCH] fix tail position in collection forms

---
 sandbox.ld      | 38 ++++++++++++++++++++++++++++++++++++--
 src/compiler.rs |  7 +++++--
 src/vm.rs       | 14 +++++++-------
 3 files changed, 48 insertions(+), 11 deletions(-)

diff --git a/sandbox.ld b/sandbox.ld
index 927e835..243f9c0 100644
--- a/sandbox.ld
+++ b/sandbox.ld
@@ -1,3 +1,37 @@
-let #{a, b, ...} = #{:a 1, :b 2, :c 3} 
+& let state = #{:position (0, 0), :heading 0, :pencolor :white}
+
+& let command = (:forward, 10)
+
+& match command with {
+& 	(:goto, (x, y)) -> assoc (state, :position, (x, y))
+& 	& (:home) -> do state > 
+& 	& 	assoc (_, :position, (0, 0)) >
+& 	& 	assoc (_, :heading, 0)
+& 	& (:clear) -> do state >
+& 	& 	assoc (state, :position, (0, 0)) >
+& 	& 	assoc (_, :heading, 0)
+& 	(:right, turns) -> update (state, :heading, add (_, turns))
+& 	(:left, turns) -> update (state, :heading, sub (_, turns))
+& 	(:forward, steps) -> {
+& 		let #{heading, position, ...} = state
+& 		let unit = heading/vector (heading)
+& 		let vect = mult (steps, unit)
+& 		update (state, :position, add (vect, _))
+& 	}
+& 	(:back, steps) -> {
+& 		let #{heading, position, ...} = state
+& 		let unit = heading/vector (heading)
+& 		let vect = mult (steps, unit)
+& 		update (state, :position, sub (_, vect))
+& 	}
+& 	& (:penup) -> assoc (state, :pendown?, false)
+& 	& (:pendown) -> assoc (state, :pendown?, true)
+& 	& (:penwidth, pixels) -> assoc (state, :penwidth, pixels)
+& 	& (:pencolor, color) -> assoc (state, :pencolor, color)
+& 	& (:setheading, heading) -> assoc (state, :heading, heading)
+& 	& (:loadstate, position, heading, visible?, pendown?, penwidth, pencolor) -> #{position, heading, visible?, pendown?, penwidth, pencolor}
+& 	& (:show) -> assoc (state, :visible?, true)
+& 	& (:hide) -> assoc (state, :visible?, false)
+& 	& (:background, _) -> state
+& }
 
-(a, b)
diff --git a/src/compiler.rs b/src/compiler.rs
index 3442df8..affaa8e 100644
--- a/src/compiler.rs
+++ b/src/compiler.rs
@@ -740,8 +740,6 @@ impl<'a> Compiler<'a> {
                 }
 
                 self.pop_n(pairs.len());
-                // self.emit_op(Op::PopN);
-                // self.emit_byte(pairs.len());
 
                 self.patch_jump(before_load_dict_idx, self.len() - before_load_dict_idx - 3);
                 self.patch_jump(jump_idx, self.len() - jump_idx - 3);
@@ -796,6 +794,7 @@ impl<'a> Compiler<'a> {
             }
             PairPattern(_, _) => unreachable!(),
             Tuple(members) => {
+                self.tail_pos = false;
                 for member in members {
                     self.visit(member);
                 }
@@ -804,6 +803,7 @@ impl<'a> Compiler<'a> {
                 self.stack_depth = self.stack_depth + 1 - members.len();
             }
             List(members) => {
+                self.tail_pos = false;
                 self.emit_op(Op::PushList);
                 self.stack_depth += 1;
                 for member in members {
@@ -817,11 +817,13 @@ impl<'a> Compiler<'a> {
                 }
             }
             LBox(name, expr) => {
+                self.tail_pos = false;
                 self.visit(expr);
                 self.emit_op(Op::PushBox);
                 self.bind(name);
             }
             Dict(pairs) => {
+                self.tail_pos = false;
                 self.emit_op(Op::PushDict);
                 self.stack_depth += 1;
                 for pair in pairs.iter().rev() {
@@ -836,6 +838,7 @@ impl<'a> Compiler<'a> {
                 }
             }
             Pair(key, value) => {
+                self.tail_pos = false;
                 self.emit_constant(Value::Keyword(key));
                 self.visit(value);
             }
diff --git a/src/vm.rs b/src/vm.rs
index 3c725f7..b442d0a 100644
--- a/src/vm.rs
+++ b/src/vm.rs
@@ -968,13 +968,13 @@ impl Vm {
                                 }
                                 _ => return self.panic("internal ludus error"),
                             };
-                            // algo:
-                            // clear the stack
-                            self.stack.truncate(self.frame.stack_base);
-                            // then pop back out to the enclosing stack frame
-                            self.frame = self.call_stack.pop().unwrap();
-                            self.ip = self.frame.ip;
-                            // finally, throw the value on the stack
+                            // // algo:
+                            // // clear the stack
+                            // self.stack.truncate(self.frame.stack_base);
+                            // // then pop back out to the enclosing stack frame
+                            // self.frame = self.call_stack.pop().unwrap();
+                            // self.ip = self.frame.ip;
+                            // // finally, throw the value on the stack
                             self.push(value);
                             println!(
                                 "=== returning to {} ===",