From d1535e945e05b4b49084127d81340d00d36b8bf3 Mon Sep 17 00:00:00 2001
From: Philippe-Cholet <phcholet@orange.fr>
Date: Mon, 12 Jun 2023 12:16:35 +0200
Subject: [PATCH] Fully replace MergePredicate by OrderingOrBool

---
 src/merge_join.rs | 55 +++++++++++++----------------------------------
 1 file changed, 15 insertions(+), 40 deletions(-)

diff --git a/src/merge_join.rs b/src/merge_join.rs
index e4f0f7500..15b17ce79 100644
--- a/src/merge_join.rs
+++ b/src/merge_join.rs
@@ -10,14 +10,6 @@ use crate::size_hint::{self, SizeHint};
 #[cfg(doc)]
 use crate::Itertools;
 
-pub trait MergePredicate<I, J> {
-    type Item;
-    fn left(left: I) -> Self::Item;
-    fn right(right: J) -> Self::Item;
-    fn merge(&mut self, left: I, right: J) -> (Option<I>, Option<J>, Self::Item);
-    fn size_hint(left: SizeHint, right: SizeHint) -> SizeHint;
-}
-
 /// Return an iterator adaptor that merge-joins items from the two base iterators in ascending order.
 ///
 /// [`IntoIterator`] enabled version of [`Itertools::merge_join_by`].
@@ -100,24 +92,6 @@ impl<I, J> OrderingOrBool<I, J> for bool {
     }
 }
 
-impl<I, J, OoB: OrderingOrBool<I, J>, F: FnMut(&I, &J) -> OoB> MergePredicate<I, J> for F {
-    type Item = OoB::MergeResult;
-    fn left(left: I) -> Self::Item {
-        OoB::left(left)
-    }
-    fn right(right: J) -> Self::Item {
-        OoB::right(right)
-    }
-    fn merge(&mut self, left: I, right: J) -> (Option<I>, Option<J>, Self::Item) {
-        let cmp_result = self(&left, &right);
-        OoB::merge(cmp_result, left, right)
-    }
-    fn size_hint(left: SizeHint, right: SizeHint) -> SizeHint {
-        OoB::size_hint(left, right)
-    }
-
-}
-
 impl<I, J, F> Clone for MergeJoinBy<I, J, F>
     where I: Iterator,
           J: Iterator,
@@ -137,20 +111,21 @@ impl<I, J, F> fmt::Debug for MergeJoinBy<I, J, F>
     debug_fmt_fields!(MergeJoinBy, left, right);
 }
 
-impl<I, J, F> Iterator for MergeJoinBy<I, J, F>
+impl<I, J, F, T> Iterator for MergeJoinBy<I, J, F>
     where I: Iterator,
           J: Iterator,
-          F: MergePredicate<I::Item, J::Item>,
+          F: FnMut(&I::Item, &J::Item) -> T,
+          T: OrderingOrBool<I::Item, J::Item>,
 {
-    type Item = F::Item;
+    type Item = T::MergeResult;
 
     fn next(&mut self) -> Option<Self::Item> {
         match (self.left.next(), self.right.next()) {
             (None, None) => None,
-            (Some(left), None) => Some(F::left(left)),
-            (None, Some(right)) => Some(F::right(right)),
+            (Some(left), None) => Some(T::left(left)),
+            (None, Some(right)) => Some(T::right(right)),
             (Some(left), Some(right)) => {
-                let (left, right, next) = self.cmp_fn.merge(left, right);
+                let (left, right, next) = (self.cmp_fn)(&left, &right).merge(left, right);
                 if let Some(left) = left {
                     self.left.put_back(left);
                 }
@@ -163,7 +138,7 @@ impl<I, J, F> Iterator for MergeJoinBy<I, J, F>
     }
 
     fn size_hint(&self) -> SizeHint {
-        F::size_hint(self.left.size_hint(), self.right.size_hint())
+        T::size_hint(self.left.size_hint(), self.right.size_hint())
     }
 
     fn count(mut self) -> usize {
@@ -175,7 +150,7 @@ impl<I, J, F> Iterator for MergeJoinBy<I, J, F>
                 (None, Some(_right)) => break count + 1 + self.right.into_parts().1.count(),
                 (Some(left), Some(right)) => {
                     count += 1;
-                    let (left, right, _) = self.cmp_fn.merge(left, right);
+                    let (left, right, _) = (self.cmp_fn)(&left, &right).merge(left, right);
                     if let Some(left) = left {
                         self.left.put_back(left);
                     }
@@ -193,17 +168,17 @@ impl<I, J, F> Iterator for MergeJoinBy<I, J, F>
             match (self.left.next(), self.right.next()) {
                 (None, None) => break previous_element,
                 (Some(left), None) => {
-                    break Some(F::left(
+                    break Some(T::left(
                         self.left.into_parts().1.last().unwrap_or(left),
                     ))
                 }
                 (None, Some(right)) => {
-                    break Some(F::right(
+                    break Some(T::right(
                         self.right.into_parts().1.last().unwrap_or(right),
                     ))
                 }
                 (Some(left), Some(right)) => {
-                    let (left, right, elem) = self.cmp_fn.merge(left, right);
+                    let (left, right, elem) = (self.cmp_fn)(&left, &right).merge(left, right);
                     previous_element = Some(elem);
                     if let Some(left) = left {
                         self.left.put_back(left);
@@ -224,10 +199,10 @@ impl<I, J, F> Iterator for MergeJoinBy<I, J, F>
             n -= 1;
             match (self.left.next(), self.right.next()) {
                 (None, None) => break None,
-                (Some(_left), None) => break self.left.nth(n).map(F::left),
-                (None, Some(_right)) => break self.right.nth(n).map(F::right),
+                (Some(_left), None) => break self.left.nth(n).map(T::left),
+                (None, Some(_right)) => break self.right.nth(n).map(T::right),
                 (Some(left), Some(right)) => {
-                    let (left, right, _) = self.cmp_fn.merge(left, right);
+                    let (left, right, _) = (self.cmp_fn)(&left, &right).merge(left, right);
                     if let Some(left) = left {
                         self.left.put_back(left);
                     }