Add an iterator for non trivial positions

Author: maxtremblay

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "sparse-bin-mat"
-version = "0.3.0"
+version = "0.4.0"
 authors = ["maxtremblay <maxtremblay>"]
 edition = "2018"
 description = "A sparse implementation of a binary matrix optimized for row operations"

src/vector/mod.rs

@@ -226,8 +226,11 @@ impl<T: Deref<Target = [usize]>> SparseBinVecBase<T> {
     /// assert_eq!(iter.next(), Some(3));
     /// assert_eq!(iter.next(), None);
     /// ```
-    pub fn non_trivial_positions<'a>(&'a self) -> impl Iterator<Item = usize> + 'a {
-        self.positions.iter().cloned()
+    pub fn non_trivial_positions<'a>(&'a self) -> NonTrivialPositions<'a> {
+        NonTrivialPositions {
+            positions: &self.positions,
+            index: 0,
+        }
     }
 
     /// Returns the concatenation of two vectors.
@@ -424,6 +427,22 @@ impl<T: Deref<Target = [usize]>> fmt::Display for SparseBinVecBase<T> {
     }
 }
 
+pub struct NonTrivialPositions<'vec> {
+    positions: &'vec [usize],
+    index: usize,
+}
+
+impl<'vec> Iterator for NonTrivialPositions<'vec> {
+    type Item = usize;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.positions.get(self.index).map(|position| {
+            self.index += 1;
+            *position
+        })
+    }
+}
+
 #[cfg(test)]
 mod test {
     use super::*;