Use is_empty

We already use is_empty in other places, so it is presumably consistent
with these.

Author: phimuemue

src/adaptors/multi_product.rs

@@ -161,7 +161,7 @@ impl<I> Iterator for MultiProduct<I>
     }
 
     fn count(self) -> usize {
-        if self.0.len() == 0 {
+        if self.0.is_empty() {
             return 0;
         }
 
@@ -183,7 +183,7 @@ impl<I> Iterator for MultiProduct<I>
 
     fn size_hint(&self) -> (usize, Option<usize>) {
         // Not ExactSizeIterator because size may be larger than usize
-        if self.0.len() == 0 {
+        if self.0.is_empty() {
             return (0, Some(0));
         }
 

src/combinations.rs

@@ -56,7 +56,7 @@ impl<I> Iterator for Combinations<I>
                 return None;
             }
             self.first = false;
-        } else if self.indices.len() == 0 {
+        } else if self.indices.is_empty() {
             return None;
         } else {
             // Scan from the end, looking for an index to increment

src/format.rs

@@ -60,7 +60,7 @@ impl<'a, I, F> fmt::Display for FormatWith<'a, I, F>
         if let Some(fst) = iter.next() {
             format(fst, &mut |disp: &dyn fmt::Display| disp.fmt(f))?;
             for elt in iter {
-                if self.sep.len() > 0 {
+                if !self.sep.is_empty() {
 
                     f.write_str(self.sep)?;
                 }
@@ -85,7 +85,7 @@ impl<'a, I> Format<'a, I>
         if let Some(fst) = iter.next() {
             cb(&fst, f)?;
             for elt in iter {
-                if self.sep.len() > 0 {
+                if !self.sep.is_empty() {
                     f.write_str(self.sep)?;
                 }
                 cb(&elt, f)?;

src/tuple_impl.rs

@@ -57,7 +57,7 @@ impl<T> Iterator for TupleBuffer<T>
 
     fn size_hint(&self) -> (usize, Option<usize>) {
         let buffer = &self.buf.as_ref()[self.cur..];
-        let len = if buffer.len() == 0 {
+        let len = if buffer.is_empty() {
             0
         } else {
             buffer.iter()