feat: upgrade to Mun v0.2.0 and buoyancy example

.gitignore

@@ -293,6 +293,7 @@ GitHub.sublime-settings
 tmtags
 
 ##### VisualStudioCode
+/.vscode
 .vscode/*
 !.vscode/settings.json
 !.vscode/tasks.json
@@ -912,3 +913,6 @@ _deps
 *.exe
 *.out
 *.app
+
+# Artifacts
+*.munlib

resources/buoyancy.mun

@@ -0,0 +1,91 @@
+extern fn log_f32(value: f32);
+
+struct SimContext {
+    sphere: Sphere,
+    water: Water,
+    gravity: f32,
+}
+
+struct Sphere {
+    radius: f32,
+    mass: f32,      // density: f32,
+    height: f32,
+    velocity: f32,
+}
+
+struct Water {
+    density: f32,
+}
+
+pub fn new_sim() -> SimContext {
+    SimContext {
+        sphere: new_sphere(),
+        water: new_water(),
+        gravity: 9.81,
+    }
+}
+
+fn new_sphere() -> Sphere {
+    let radius = 1.0;
+    let density = 250.0;
+
+    let volume = calc_sphere_volume(radius);
+    let mass = density * volume;
+
+    Sphere {
+        radius,
+        mass,
+        height: 1.0,
+        velocity: 0.0,
+    }
+}
+
+fn new_water() -> Water {
+    Water {
+        density: 1000.0,
+    }
+}
+
+fn calc_submerged_ratio(s: Sphere) -> f32 {
+    let bottom = s.height - s.radius;
+    let diameter = 2.0 * s.radius;
+    if bottom >= 0.0 {
+        0.0
+    } else if bottom <= -diameter {
+        1.0
+    } else {
+        -bottom / diameter
+    }
+}
+
+fn calc_sphere_volume(radius: f32) -> f32 {
+    let pi = 3.1415926535897;
+    let r = radius;
+
+    3.0/4.0 * pi * r * r * r
+}
+
+fn calc_buoyancy_force(s: Sphere, w: Water, gravity: f32, submerged_ratio: f32) -> f32 {
+    let volume = calc_sphere_volume(s.radius);
+    volume * submerged_ratio * w.density * gravity
+}
+
+pub fn sim_update(ctx: SimContext, elapsed_secs: f32) {
+    let submerged_ratio = calc_submerged_ratio(ctx.sphere);
+    if submerged_ratio > 0.0 {
+        let buoyancy_force = calc_buoyancy_force(
+            ctx.sphere,
+            ctx.water,
+            ctx.gravity,
+            submerged_ratio
+        );
+        let buoyancy_acc = buoyancy_force / ctx.sphere.mass;
+        ctx.sphere.velocity += buoyancy_acc * elapsed_secs;
+    }
+
+    ctx.sphere.velocity -= ctx.gravity * elapsed_secs;
+
+    ctx.sphere.height += ctx.sphere.velocity * elapsed_secs;
+
+    log_f32(ctx.sphere.height);
+}

src/main.cc

@@ -1,34 +1,55 @@
 #include <iostream>
 #include <string>
 
-#include "mun/runtime.h"
+#include "mun/mun.h"
+
+extern "C" {
+void log_f32(float value) { std::cout << std::to_string(value) << std::endl; }
+}
 
 // How to run?
 // 1. On the CLI, navigate to the `example-cpp` directory.
-// 2. Run the compiler daemon from the CLI: `/path/to/mun build resources/fibonacci.mun --watch`
-// 3. Run the application from the CLI: `main /path/to/fibonacci.dll`
+// 2. Run the compiler daemon from the CLI:
+//    `/path/to/mun build resources/buoyancy.mun --watch`
+// 3. Run the application from the CLI:
+//    `main /path/to/buoyancy.munlib`
 int main(int argc, char* argv[]) {
     if (argc < 2) {
         return 1;
     }
-
     std::cout << "lib: " << argv[1] << std::endl;
 
+    mun::RuntimeOptions options;
+    options.functions.emplace_back(mun::RuntimeFunction("log_f32", log_f32));
+
     mun::Error error;
-    if (auto runtime = mun::make_runtime(argv[1], &error)) {
+    if (auto runtime = mun::make_runtime(argv[1], options, &error)) {
+        auto ctx = mun::invoke_fn<mun::StructRef>(*runtime, "new_sim").wait();
+
+        using clock_t = std::chrono::high_resolution_clock;
+        using fsec_t = std::chrono::duration<float>;
+
+        auto previous = clock_t::now();
+        constexpr auto FRAME_TIME = std::chrono::milliseconds(40);
         while (true) {
-            auto n = mun::invoke_fn<int64_t>(*runtime, "nth").wait();
-            auto result = mun::invoke_fn<int64_t>(*runtime, "fibonacci", n).wait();
+            std::this_thread::sleep_until(previous + FRAME_TIME);
+
+            const auto now = clock_t::now();
+            const auto elapsed =
+                std::chrono::duration_cast<fsec_t>(now - previous);
 
-            std::cout << "fibonacci(" << std::to_string(n) << ") = " << result << std::endl;
+            mun::invoke_fn<void>(*runtime, "sim_update", ctx, elapsed.count()).wait();
+            previous = now;
 
             mun::Error update_error;
             if (!runtime->update(&update_error) && update_error) {
-                std::cerr << "Failed to update runtime due to error: " << update_error.message() << std::endl;
+                std::cerr << "Failed to update runtime due to error: "
+                          << update_error.message() << std::endl;
             }
         }
     }
 
-    std::cerr << "Failed to construct Mun runtime due to error: " << error.message() << std::endl;
+    std::cerr << "Failed to construct Mun runtime due to error: "
+              << error.message() << std::endl;
     return 2;
 }