From 8614f978ea9021036f8089360a47c0c37a9a73ed Mon Sep 17 00:00:00 2001
From: Andre Wagner <WagnerAndre@JohnDeere.com>
Date: Tue, 5 May 2026 09:40:22 -0500
Subject: [PATCH] .

---
 lua-temp/tests.lua    |  32 ++++++++++++
 lua-temp/tyche-vm.lua | 118 ++++++++++++++++++++++++++++++++++++++++--
 2 files changed, 147 insertions(+), 3 deletions(-)

diff --git a/lua-temp/tests.lua b/lua-temp/tests.lua
index 84b1732..99b633f 100644
--- a/lua-temp/tests.lua
+++ b/lua-temp/tests.lua
@@ -84,6 +84,11 @@ do
     assert_eq(stack[1], 20)
     assert_eq(stack[-1], 30)
     assert_eq(stack[-2], 20)
+
+    stack:pop()
+    stack:pop()
+    stack:pop()
+    assert_eq(#stack, 0)
 end
 
 do
@@ -110,4 +115,31 @@ do
     assert_eq(stack[-2], 10)
 end
 
+----------------------
+--                  --
+--     VM STACK     --
+--                  --
+----------------------
+
+do
+    local vm = VM:new()
+    local bytecode = assemble [[
+        .func 0
+            pushi   2
+            pushi   3
+            sum
+            ret
+    ]]
+    vm:load(bytecode)
+
+    assert_eq(vm:stack_sz(), 1)
+    assert_eq(vm:is(-1, 'function'), true)
+
+    vm:call(0)
+
+    assert_eq(vm:stack_sz(), 1)
+    assert_eq(vm:is(-1, 'integer'))
+    assert_eq(vm:to_integer(-1), 5)
+end
+
 print('End.')
\ No newline at end of file
diff --git a/lua-temp/tyche-vm.lua b/lua-temp/tyche-vm.lua
index cf07726..d3d6c8d 100644
--- a/lua-temp/tyche-vm.lua
+++ b/lua-temp/tyche-vm.lua
@@ -27,14 +27,14 @@ function Stack:push(value)
 end
 
 function Stack:pop(value)
-    if #self.stack <= self:top_fps() then error("Stack underflow") end
+    if #self.stack < self:top_fps() then error("Stack underflow") end
     local v = self.stack[#self.stack]
     self.stack[#self.stack] = nil
     return v
 end
 
 function Stack:peek(value)
-    if #self.stack <= self:top_fps() then error("Stack underflow") end
+    if #self.stack < self:top_fps() then error("Stack underflow") end
     return self.stack[#self.stack]
 end
 
@@ -91,6 +91,35 @@ function Stack:debug()
     return table.concat(ss)
 end
 
+----------------------
+--                  --
+--      CODE        --
+--                  --
+----------------------
+
+local Code = {}
+Code.__index = Code
+
+function Code.new()
+    return setmetatable({
+        bytecode = nil
+    }, Code)
+end
+
+function Code:load(bytecode)
+    -- TODO - what if there's code already loaded?
+    self.bytecode = bytecode
+    return 0   -- main function
+end
+
+function Code:next_instruction(function_id, pc)
+    return {
+        operator = self.bytecode.functions[function_id][pc][1],
+        operand = self.bytecode.functions[function_id][pc][2],
+        instruction_size = 1,
+    }
+end
+
 ----------------------
 --                  --
 --       VM         --
@@ -102,8 +131,91 @@ VM.__index = VM
 
 function VM.new()
     return setmetatable({
-        stack = Stack.new()
+        stack = Stack.new(),
+        code = Code.new(),
+        loc = {},
     }, VM)
 end
 
+--
+-- code management
+--
+
+function VM:load(bytecode)
+    local f_id = self.code:load(bytecode)
+    self.stack:push({ type = 'function', value = f_id })
+    return self
+end
+
+--
+-- stack management
+--
+
+function VM:push_integer(n)
+    self.stack:push({ type = 'integer', value = n })
+end
+
+--
+-- information
+--
+
+function VM:stack_sz()
+    return #self.stack
+end
+
+function VM:is(idx, type)
+    return self.stack[idx].type == type
+end
+
+function VM:to_integer(idx)
+    local value = self.stack[idx]
+    if value.type ~= 'integer' then error("Type error: not an integer") end
+    return value.value
+end
+
+--
+-- code execution
+--
+
+function VM:call(n_pars)
+    local f = self.stack:pop()
+    if f.type ~= 'function' then error("Type error: expected function") end
+    table.insert(self.loc, {
+        f_id = f.value,
+        pc = 1
+    })
+    self.stack:push_fp()
+    self:_run_until_return()  -- execute code
+    table.remove(self.loc)
+    return self
+end
+
+function VM:_run_until_return()
+    local level = self.stack:fp_level()
+    while self.stack:fp_level() >= level do
+        self:_step()
+    end
+end
+
+function VM:_step()
+    local loc = self.loc[#self.loc]
+    local op = self.code:next_instruction(loc.f_id, loc.pc)
+    print(loc.f_id .. ':' .. loc.pc .. '   ' .. op.operator .. ' ' .. (op.operand and op.operand or ''))
+
+    if op.operator == 'pushi' then
+        self:push_integer(op.operand)
+    elseif op.operator == 'sum' then
+        self:push_integer(self.stack:pop().value + self.stack:pop().value)
+    elseif op.operator == 'ret' then
+        local v = self.stack:pop()
+        self.stack:pop_fp()
+        self.stack:push(v)
+        return
+    else
+        error("Unknown operator '" .. tostring(op.operator) .. "'")
+    end
+
+    loc.pc = loc.pc + op.instruction_size
+end
+
 return VM
\ No newline at end of file