diff --git a/src/bbp.rs b/src/bbp.rs
index 9217cc4..f00aef9 100644
--- a/src/bbp.rs
+++ b/src/bbp.rs
@@ -1,17 +1,10 @@
 pub fn get_byte(id: i32) -> u8 {
     let pid : f64 = 4.0 * series(1, id) - 2.0 * series(4, id) - series(5, id) - series(6, id);
 
-    let mut y : f64 = (pid - (pid as i32) as f64 + 1.0).abs(); // TODO use .trunc() instead
+    let y : f64 = (pid - (pid as i32) as f64 + 1.0).abs(); // TODO use .trunc() instead
+    let y = 16.0 * (y - y.floor());
 
-    y = 16.0 * (y - y.floor()); // TODO use .trunc() instead of floor?
-
-    let first : u8 = y as u8;
-
-    y = 16.0 * (y - y.floor()); // TODO use .trunc() instead of floor?
-
-    let second : u8 = y as u8;
-
-    (first << 4) | second
+    ((y as u8) << 4) | (16.0 * (y - y.floor())) as u8
 }
 
 fn series(m: i32, id: i32) -> f64 {
@@ -26,7 +19,7 @@ fn series(m: i32, id: i32) -> f64 {
       t = expm((id - k) as f64, ak);
 
       s += t / ak;
-      s -= (s as i32) as f64; // TODO: use .truc() instead.
+      s -= s.trunc();
     }
 
     for k in id..id + 101 {
@@ -38,7 +31,7 @@ fn series(m: i32, id: i32) -> f64 {
       }
 
       s += t;
-      s -= (s as i32) as f64; // TODO: use .truc() instead.
+      s -= s.trunc();
     }
 
     s
@@ -70,22 +63,22 @@ fn expm(p: f64, ak: f64) -> f64 {
     }
 
     let mut pt = TP[i - 1];
-    let mut p1 : f64 = p; // TODO: use p instead of p1?
+    let mut p = p;
     let mut r : f64 = 1.0;
 
     for _ in 1..i + 1 {
-      if p1 >= pt {
+      if p >= pt {
         r = 16.0 * r;
-        r = r - ((r / ak) as i32) as f64 * ak; // TODO: use .truc() instead.
+        r = r - (r / ak).trunc() * ak;
 
-        p1 -= pt;
+        p -= pt;
       }
 
       pt = 0.5 * pt;
 
       if pt >= 1.0 {
         r *= r;
-        r -= ((r / ak) as i32) as f64 * ak; // TODO: use .truc() instead.
+        r -= (r / ak).trunc() * ak;
       }
     }
 
diff --git a/src/main.rs b/src/main.rs
index 3608f42..2c5bcd0 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -18,6 +18,11 @@ use pbr::{ProgressBar, Units};
 
 mod bbp;
 
+fn print_usage(program: &str, opts: Options) {
+    let brief = format!("Usage: {} [option] INPUT OUTPUT", program);
+    print!("{}", opts.usage(&brief));
+}
+
 fn main() {
     let args: Vec<String> = env::args().collect();
     let program = args[0].clone();
@@ -29,14 +34,28 @@ fn main() {
     opts.optflag("h", "help", "display this help and exit");
 
     let matches = match opts.parse(&args[1..]) {
-        Ok(m) => { m }
-        Err(f) => { panic!(f.to_string()) }
+        Ok(m) => m,
+        Err(_) => {
+            print_usage(&program, opts);
+            std::process::exit(1);
+        }
     };
 
     if matches.opt_present("help") {
-        let brief = format!("Usage: {} [option] INPUT OUTPUT", program);
-        print!("{}", opts.usage(&brief));
-        return;
+        print_usage(&program, opts);
+        std::process::exit(0);
+    }
+
+    if matches.free.len() == 1 {
+        println!("Missing operand: OUTPUT");
+        println!("Try `{} --help` for more information.", program);
+        std::process::exit(1);
+    }
+
+    if matches.free.len() == 0 {
+        println!("Missing operand: INPUT OUTPUT");
+        println!("Try `{} --help` for more information.", program);
+        std::process::exit(1);
     }
 
     if matches.opt_present("c") {
@@ -44,8 +63,7 @@ fn main() {
         let output = &matches.free[1];
 
         compress(&input, &output);
-    }
-    else if matches.opt_present("d") {
+    } else if matches.opt_present("d") {
         let input = &matches.free[0];
         let output = &matches.free[1];