Can format Lengths.

Author: thejpster

examples/format_test.rs

@@ -1,7 +1,11 @@
 extern crate measurements;
 use measurements::Temperature;
+use measurements::Length;
 fn main() {
 	let t = Temperature::from_celsius(0.1);
+	let d = Length::from_meters(10000.1);
 	println!("{0:.9} outside", t);
-	println!("{0:.9} outside", t.as_celsius());
+	println!("{0:.9} C outside", t.as_celsius());
+	println!("{0:.3} away", d);
+	println!("{0:.3} m away", d.as_meters());
 }

src/length.rs

@@ -157,6 +157,8 @@ implement_measurement! { Length }
 
 impl ::std::fmt::Display for Length {
     fn fmt(&self, f: &mut ::std::fmt::Formatter) -> ::std::fmt::Result {
-        write!(f, "{:.1} m", self.as_meters())
+        let p = f.precision().unwrap_or(1);
+        let w = f.width().unwrap_or(0);
+        write!(f, "{value:width$.prec$}\u{00A0}m", prec=p, width=w, value=self.as_meters())
     }
 }