Implemented core functionality

src/main.rs

@@ -3,7 +3,40 @@ extern crate clap;
 
 fn main() {
     use clap::App;
-    
+
     let yml = load_yaml!("arguments.yml");
     let m = App::from_yaml(yml).get_matches();
+
+    if let Some(delay) = m.value_of("DELAY") {
+        match delay.parse() {
+            Ok(time) => print_delay(m.value_of("STRING").unwrap(), time),
+            Err(_) => unreachable!(),
+        }
+    } else {
+        print_no_delay(m.value_of("STRING").unwrap());
+    }
+}
+
+fn print_delay(text: &str, delay: f64) {
+    use std::thread::sleep;
+    use std::time::{Duration,Instant};
+
+    let mut time = Instant::now();
+    let secs = delay as u64;
+    let nanos = ((delay - secs as f64) * 1e9) as u32;
+    let duration = Duration::new(secs, nanos);
+    loop {
+        println!("{}", text);
+        time += duration;
+        let now = Instant::now();
+        if time > now {
+            sleep(time.duration_since(now));
+        }
+    }
+}
+
+fn print_no_delay(text: &str) {
+    loop {
+        println!("{}", text);
+    }
 }