update docs for VecExtns

src/utils/vec_exns.rs

@@ -1,14 +1,16 @@
 //! Extend functionality of Rust vectors.
 
+/// This trait provides additionaly functionality for Rust vectors
 pub trait VecExtns<T> {
-    // Insert a new element and get back its index in the container.
+    /// Insert a new element and get back its index in the container.
     fn push_back(&mut self, t: T) -> usize;
-    // Insert a new element, constructed by calling `ctor`,
-    // and get back its index in the container. `ctor` will
-    // receve the index as a parameter. This is useful when the
-    // element inserted needs to know its index.
+    /// Insert a new element, constructed by calling `ctor`,
+    /// and get back its index in the container. `ctor` will
+    /// receve the index as a parameter. This is useful when the
+    /// element inserted needs to know its index.
     fn push_back_with(&mut self, ctor: impl FnMut(usize) -> T) -> usize;
-    // Create and initialize a new vector.
+
+    /// Create and initialize a new vector.
     fn new_init<U: FnMut(usize) -> T>(size: usize, initf: U) -> Vec<T>;
 }