From 04f065359585b858a069ffd5019c6a74a11e0da0 Mon Sep 17 00:00:00 2001
From: Kayne Ruse <kayneruse@gmail.com>
Date: Sat, 16 Nov 2024 17:57:41 +1100
Subject: [PATCH] Planned control flow statements

---
 .notes/control-flow-opcodes.txt | 120 ++++++++++++++++++++++++++++++++
 1 file changed, 120 insertions(+)
 create mode 100644 .notes/control-flow-opcodes.txt

diff --git a/.notes/control-flow-opcodes.txt b/.notes/control-flow-opcodes.txt
new file mode 100644
index 0000000..5ea6673
--- /dev/null
+++ b/.notes/control-flow-opcodes.txt
@@ -0,0 +1,120 @@
+types:
+	if-then-else
+	ternary ?:
+	while
+	do-while
+	for
+	foreach (compounds)
+	switch-case-default (and continue/break?)
+	continue
+	break
+
+if-then:
+	cond-branch
+	if false jump end
+	{
+		then-branch
+	}
+	end
+
+if-then-else: (also ternary)
+	cond-branch
+	if false jump else
+	{
+		then-branch
+	}
+	jump end
+	{
+		else-branch
+	}
+	end
+
+while:
+	begin
+	cond-branch
+	if false jump end
+	{
+		then-branch
+	}
+	jump begin
+	end
+
+do-while:
+	begin
+	{
+		then-branch
+	}
+	cond-branch
+	if true jump begin
+	end
+
+for:
+	{
+		pre-branch
+		begin
+		cond-branch
+		if false jump end
+		{
+			then-branch
+		}
+		post-branch
+		jump begin
+		end
+	}
+
+foreach:
+	...needs more planning
+
+switch-case-default:
+	...needs more planning
+
+continue:
+	jump begin
+	unwind scopes
+
+break:
+	jump end
+	unwind scopes
+
+---
+
+Notes:
+	The additional scope in 'for' is to safely encapsulate pre-branch, as variables can be declared here.
+	do-while's 'end' is only there for the break/continue keywords.
+	break and continue will also unwind scopes, up to the innermost control-flow level.
+
+break/continue within nested scopes:
+	Because control flows can be nested, a stack of scope depths may be needed for break/continue...
+	However, this would get more complicated with closures.
+	To fix this, scopes may need to remember their own depth, and the depth of the innermost control-flow level.
+	If a scope's depth is 10 and the inner control-flow-level is 7, then calling break/continue will jump AND unwind to the inner control-flow level.
+
+---
+
+JUMP word:
+	opcode
+	type (absolute, relative)
+	conditional (always, if_true, if_false)
+	-
+
+	value
+
+absolute:
+	"value" is relative to the code sections starting position
+
+relative:
+	"value" is relative to the program counter, after this opcode has been read from the bytecode
+
+always:
+	Always jump
+
+if_true:
+	pop the stack top
+	if the popped value is true, then jump
+	else ignore
+
+if_false:
+	pop the stack top
+	if the popped value is true, then ignore
+	else jump
+