From 313ed45c6942846c138b495c4140c6e49f7189e5 Mon Sep 17 00:00:00 2001
From: VegOwOtenks <vegowotenks@jossco.de>
Date: Thu, 22 May 2025 20:22:48 +0200
Subject: [PATCH] feat: heterogeneous-list with reverse!

---
 .gitignore   |  1 +
 Cargo.lock   |  7 +++++
 Cargo.toml   |  6 ++++
 src/hlist.rs | 83 ++++++++++++++++++++++++++++++++++++++++++++++++++++
 src/main.rs  | 38 ++++++++++++++++++++++++
 5 files changed, 135 insertions(+)
 create mode 100644 .gitignore
 create mode 100644 Cargo.lock
 create mode 100644 Cargo.toml
 create mode 100644 src/hlist.rs
 create mode 100644 src/main.rs

diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..ea8c4bf
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1 @@
+/target
diff --git a/Cargo.lock b/Cargo.lock
new file mode 100644
index 0000000..bb8d44a
--- /dev/null
+++ b/Cargo.lock
@@ -0,0 +1,7 @@
+# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 4
+
+[[package]]
+name = "heterogeneous-list"
+version = "0.1.0"
diff --git a/Cargo.toml b/Cargo.toml
new file mode 100644
index 0000000..871faf9
--- /dev/null
+++ b/Cargo.toml
@@ -0,0 +1,6 @@
+[package]
+name = "heterogeneous-list"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
diff --git a/src/hlist.rs b/src/hlist.rs
new file mode 100644
index 0000000..1ea1b83
--- /dev/null
+++ b/src/hlist.rs
@@ -0,0 +1,83 @@
+use hidden::HList_;
+
+mod hidden {
+    pub trait HList_ {}
+}
+
+pub trait Reversed<Cont>
+{
+    type Output: HList_;
+    fn reversed_prepend(self, cont: Cont) -> Self::Output;
+}
+
+impl<Cont> Reversed<Cont> for Nil
+    where Cont: HList_
+{
+    type Output = Cont;
+
+    fn reversed_prepend(self, cont: Cont) -> Self::Output {
+        cont
+    }
+}
+
+impl<Cont, Item, Rest> Reversed<Cont> for Cons<Item, Rest>
+    where 
+        Cont: HList_,
+        Rest: HList_ + Reversed<Cons<Item, Cont>>,
+        Self: HList_,
+        Cons<Item, Cont>: HList_
+{
+    type Output = <Rest as Reversed<Cons<Item, Cont>>>::Output;
+
+    fn reversed_prepend(self, cont: Cont) -> Self::Output {
+        self.1.reversed_prepend(Cons(self.0, cont))
+    }
+
+}
+
+pub trait HList
+    where 
+        Self: Sized + HList_ + Reversed<Nil> {
+    fn prepend<T>(self, value: T) -> Cons<T, Self> {
+        Cons(value, self)
+    }
+
+    type Reversed;
+    fn reversed(self) -> Self::Reversed;
+}
+impl HList for Nil {
+
+    type Reversed = Self::Output;
+
+    fn reversed(self) -> Nil{
+        Nil
+    }
+}
+impl<Item, Rest> HList for Cons<Item, Rest> 
+    where 
+        Rest: HList_,
+        Self: Reversed<Nil>
+{
+    type Reversed = Self::Output;
+    fn reversed(self) -> Self::Output {
+        self.reversed_prepend(Nil)
+    }
+}
+
+#[derive(Debug, Default, Clone, Copy, PartialEq, PartialOrd, Ord, Eq, Hash)]
+pub struct Cons<Item, Rest: HList_>(pub Item, pub Rest);
+impl<Item, Rest> HList_ for Cons<Item , Rest> 
+    where Rest: HList_ {}
+impl<Item, Rest: HList_> Cons<Item, Rest> {
+    pub fn uncons(self) -> (Item, Rest) {
+        (self.0, self.1)
+    }
+
+    pub fn head(&self) -> &Item {
+        &self.0
+    }
+}
+
+#[derive(Debug, Default, Clone, Copy)]
+pub struct Nil;
+impl HList_ for Nil {}
diff --git a/src/main.rs b/src/main.rs
new file mode 100644
index 0000000..3282098
--- /dev/null
+++ b/src/main.rs
@@ -0,0 +1,38 @@
+use crate::hlist::HList;
+use hlist::Nil;
+
+pub mod hlist;
+
+fn main() {
+    let x = Nil
+.prepend(0)
+.prepend(1)
+.prepend(2)
+.prepend(3)
+.prepend(4)
+.prepend(5)
+.prepend(6)
+.prepend(7)
+.prepend(8)
+.prepend(9)
+.prepend(10)
+.prepend(11)
+.prepend(12)
+.prepend(13)
+.prepend(14)
+.prepend(15)
+.prepend(16)
+.prepend(17)
+.prepend(18)
+.prepend(19)
+.prepend(20)
+.prepend(21)
+.prepend(22)
+.prepend(23)
+.prepend(24)
+.prepend(25);
+    println!("{x:#?}");
+    let y = x.reversed();
+    println!("{y:#?}");
+}
+