From 43ef82ca9c53bdb50f34feba97c133183426b7f6 Mon Sep 17 00:00:00 2001
From: Albin Chaboissier <chalbin73@gmail.com>
Date: Thu, 23 Oct 2025 21:46:32 +0200
Subject: [PATCH] Adds binary operator

---
 src/main.rs             |  2 +-
 src/stream.rs           |  2 ++
 src/stream_operators.rs | 39 +++++++++++++++++++++++++++++++--------
 3 files changed, 34 insertions(+), 9 deletions(-)

diff --git a/src/main.rs b/src/main.rs
index f96f5f2..2c03de6 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -32,7 +32,7 @@ fn main() {
         }
     });
 
-    let (adder, out) = stream_operators::StreamAdder::new(a_rx, b_rx);
+    let (_adder, out) = stream_operators::BinaryOperator::new(a_rx, b_rx, |a, b| a + b);
 
     {
         loop {
diff --git a/src/stream.rs b/src/stream.rs
index 5d52967..ff09eaf 100644
--- a/src/stream.rs
+++ b/src/stream.rs
@@ -201,6 +201,8 @@ impl<'a, T: Copy> Iterator for StreamReaderIter<'a, T> {
         if self.current_guard.is_none()
             || self.current_index == self.current_guard.as_ref().unwrap().len()
         {
+            // Previous guard needs to be explicitly dropped otherwise the "read" call will
+            // happen before the lock is dropped
             if self.current_guard.is_some() {
                 let old = self.current_guard.take();
                 drop(old);
diff --git a/src/stream_operators.rs b/src/stream_operators.rs
index e693efc..be98a3a 100644
--- a/src/stream_operators.rs
+++ b/src/stream_operators.rs
@@ -1,23 +1,26 @@
 use std::ops::Add;
 
-use crate::stream::{StreamReader, stream};
+use crate::stream::{StreamReader, StreamWriter, stream};
 
-pub struct StreamAdder<T> {
-    _phantom: std::marker::PhantomData<T>,
+pub struct BinaryOperator<Ia, Ib, O> {
+    _phantom: std::marker::PhantomData<(Ia, Ib, O)>,
 }
 
-impl<T: Add<T, Output = T> + Copy + 'static> StreamAdder<T> {
-    pub fn new(input_a: StreamReader<T>, input_b: StreamReader<T>) -> (Self, StreamReader<T>) {
-        let (mut writer, reader) = stream::<T>(1024);
+impl<Ia: Copy + 'static, Ib: Copy + 'static, O: 'static> BinaryOperator<Ia, Ib, O> {
+    pub fn new(
+        input_a: StreamReader<Ia>,
+        input_b: StreamReader<Ib>,
+        oper: fn(Ia, Ib) -> O,
+    ) -> (Self, StreamReader<O>) {
+        let (mut writer, reader) = stream::<O>(1024);
         std::thread::spawn(move || {
-            //let mut writer = writer;
             let mut iter1 = input_a.iter();
             let mut iter2 = input_b.iter();
             loop {
                 let mut write = writer.write();
                 let len = write.len();
                 for i in 0..len {
-                    write[i].write(iter1.next().unwrap() + iter2.next().unwrap());
+                    write[i].write(oper(iter1.next().unwrap(), iter2.next().unwrap()));
                 }
                 write.swap(len);
             }
@@ -30,3 +33,23 @@ impl<T: Add<T, Output = T> + Copy + 'static> StreamAdder<T> {
         )
     }
 }
+
+pub struct StreamAdder<Ia, Ib, O> {
+    _bin_op: BinaryOperator<Ia, Ib, O>,
+    _phantom: std::marker::PhantomData<(Ia, Ib, O)>,
+}
+
+impl<Ia: Add<Ib, Output = O> + Copy + 'static, Ib: Copy + 'static, O: 'static>
+    StreamAdder<Ia, Ib, O>
+{
+    pub fn new(input_a: StreamReader<Ia>, input_b: StreamReader<Ib>) -> (Self, StreamReader<O>) {
+        let (_bin_op, reader) = BinaryOperator::new(input_a, input_b, |a, b| a + b);
+        (
+            Self {
+                _phantom: Default::default(),
+                _bin_op,
+            },
+            reader,
+        )
+    }
+}