From 225d1d7f3a047d696b671078e09a15cc8dd2654c Mon Sep 17 00:00:00 2001
From: colin <colin@uninsane.org>
Date: Wed, 20 Jul 2022 01:37:33 -0700
Subject: [PATCH] coremem_types: implement a list type wherein we can hope to
 implement enum-like types on gpu

---
 crates/types/src/compound.rs | 141 +++++++++++++++++++++++++++++++++++
 crates/types/src/lib.rs      |   1 +
 2 files changed, 142 insertions(+)
 create mode 100644 crates/types/src/compound.rs

diff --git a/crates/types/src/compound.rs b/crates/types/src/compound.rs
new file mode 100644
index 0000000..064f876
--- /dev/null
+++ b/crates/types/src/compound.rs
@@ -0,0 +1,141 @@
+
+#[derive(Copy, Clone, Default, PartialEq)]
+struct Null;
+
+#[derive(Copy, Clone, Default, PartialEq)]
+struct LLNode<E, N> {
+    e: E,
+    // Null or LLNode
+    next: N,
+}
+
+impl<E> LLNode<E, Null> {
+    fn new(e: E) -> Self {
+        Self {
+            e,
+            next: Null,
+        }
+    }
+}
+
+impl<E, N> LLNode<E, N> {
+    fn prepend<P>(self, e: P) -> LLNode<P, Self> {
+        LLNode {
+            e,
+            next: self
+        }
+    }
+}
+
+trait ListOp<F, L> {
+    fn apply(&self, f: F);
+}
+
+trait ElemCallable<T> {
+    fn call(&self, el: &T);
+}
+
+impl<F: ElemCallable<E>, E, N: ListOp<F, N>> ListOp<F, LLNode<E, N>> for LLNode<E, N> {
+    fn apply(&self, f: F) {
+        f.call(&self.e);
+        self.next.apply(f)
+    }
+}
+
+impl<F> ListOp<F, Null> for Null {
+    fn apply(&self, _f: F) { }
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use core::cell::Cell;
+
+    #[derive(Default)]
+    struct ApplyAccumulator<T> {
+        delayed0: Cell<T>,
+        delayed1: Cell<T>,
+        delayed2: Cell<T>,
+    }
+
+    impl ElemCallable<u32> for &ApplyAccumulator<u32> {
+        fn call(&self, el: &u32) {
+            self.delayed2.set(
+                self.delayed1.replace(
+                    self.delayed0.replace(*el)
+                )
+            )
+        }
+
+    }
+
+    #[test]
+    fn test_apply_single() {
+        let list = LLNode::new(5u32);
+        let acc = ApplyAccumulator::default();
+        list.apply(&acc);
+        
+        assert_eq!(acc.delayed1.into_inner(), 0);
+        assert_eq!(acc.delayed0.into_inner(), 5);
+    }
+
+    #[derive(Copy, Clone, Default, Debug, PartialEq)]
+    struct V0(u32);
+    #[derive(Copy, Clone, Default, Debug, PartialEq)]
+    struct V1(f32);
+    #[derive(Copy, Clone, Default, Debug, PartialEq)]
+    struct Flat {
+        v0: V0,
+        v1: V1,
+    }
+
+    trait Variant {
+        fn to_flat(&self) -> Flat;
+    }
+    impl Variant for V0 {
+        fn to_flat(&self) -> Flat {
+            Flat { v0: *self, ..Default::default() }
+        }
+    }
+    impl Variant for V1 {
+        fn to_flat(&self) -> Flat {
+            Flat { v1: *self, ..Default::default() }
+        }
+    }
+
+    impl<T: Variant> ElemCallable<T> for &ApplyAccumulator<Flat> {
+        fn call(&self, el: &T) {
+            self.delayed2.set(
+                self.delayed1.replace(
+                    self.delayed0.replace(el.to_flat())
+                )
+            )
+        }
+    }
+
+    #[test]
+    fn test_apply_2() {
+        let list = LLNode::new(V0(5u32))
+            .prepend(V1(4f32));
+        let acc = ApplyAccumulator::default();
+        list.apply(&acc);
+        
+        assert_eq!(acc.delayed2.into_inner(), Flat::default());
+        assert_eq!(acc.delayed1.into_inner(), V1(4f32).to_flat());
+        assert_eq!(acc.delayed0.into_inner(), V0(5u32).to_flat());
+    }
+
+    #[test]
+    fn test_apply_3() {
+        let list = LLNode::new(V0(5u32))
+            .prepend(V1(4f32))
+            .prepend(V0(2u32));
+        let acc = ApplyAccumulator::default();
+        list.apply(&acc);
+        
+        assert_eq!(acc.delayed2.into_inner(), V0(2u32).to_flat());
+        assert_eq!(acc.delayed1.into_inner(), V1(4f32).to_flat());
+        assert_eq!(acc.delayed0.into_inner(), V0(5u32).to_flat());
+
+    }
+}
diff --git a/crates/types/src/lib.rs b/crates/types/src/lib.rs
index f2e1c48..08c81b0 100644
--- a/crates/types/src/lib.rs
+++ b/crates/types/src/lib.rs
@@ -1,6 +1,7 @@
 #![no_std]
 #![feature(core_intrinsics)]
 
+mod compound;
 pub mod mat;
 pub mod real;
 pub mod vec;