add outputs

iter/src/main.rs

@@ -27,28 +27,51 @@ fn main() {
     test_001();
     test_002();
     test_003();
+    test_004();
 }
 
+// -> 10 11 12 13 14
 fn test_001() {
     println!("## test001");
     let seq = Seq::new(10, 15);
+    print!("->");
     for a in seq {
-        println!("-> {}", a);
+        print!(" {}", a);
     }
+    println!();
 }
 
+// -> 10 11 12 13 14
 fn test_002() {
     println!("## test002");
     let mut seq = Seq::new(10, 15);
+    print!("->");
     while let Some(a) = seq.next() {
-        println!("-> {}", a);
+        print!(" {}", a);
     }
+    println!();
 }
 
+// -> 10 11 12
 fn test_003() {
     println!("## test003");
     let mut seq = Seq::new(10, 15).take(3);
+    print!("->");
     while let Some(a) = seq.next() {
-        println!("-> {}", a);
+        print!(" {}", a);
     }
+    println!();
+}
+
+// -> 10
+// -> 10 11 12 13 14
+fn test_004() {
+    println!("## test004");
+    let mut seq = Seq::new(10, 15).peekable();
+    println!("-> {}", seq.peek().unwrap());
+    print!("->");
+    while let Some(a) = seq.next() {
+        print!(" {}", a);
+    }
+    println!();
 }