Provide a basic default implementation of History

examples/history.rs

@@ -9,6 +9,10 @@ fn main() {
 
     let mut history = MyHistory::default();
 
+    /// We can also use `Vec` or `VecDeque` directly for a simple infinite history.
+    // let mut history = Vec::new();
+    // let mut history = VecDeque::new();
+
     loop {
         if let Ok(cmd) = Input::<String>::with_theme(&ColorfulTheme::default())
             .with_prompt("dialoguer")

src/history.rs

@@ -1,3 +1,5 @@
+use std::collections::VecDeque;
+
 /// Trait for history handling.
 pub trait History<T> {
     /// This is called with the current position that should
@@ -13,3 +15,13 @@ pub trait History<T> {
     /// is implemented as a FIFO queue.
     fn write(&mut self, val: &T);
 }
+
+impl<T: ToString> History<T> for VecDeque<String> {
+    fn read(&self, pos: usize) -> Option<String> {
+        self.get(pos).cloned()
+    }
+
+    fn write(&mut self, val: &T) {
+        self.push_front(val.to_string())
+    }
+}