Fixed mph/mpg behavior

src/parser/pretoken.rs

@@ -78,6 +78,8 @@ impl PreToken {
 					"π"|"pi" => { Some(Constant::Pi)},
 					"e" => { Some(Constant::E) },
 					"phi"|"φ" => { Some(Constant::Phi) },
+					"mpg" => { Some(Constant::MPG) },
+					"mph" => { Some(Constant::MPH) },
 					_ => { None }
 				};
 

src/parser/token/constant.rs

@@ -1,17 +1,27 @@
 #[derive(Debug)]
 #[derive(Clone)]
 pub enum Constant {
+	// Fake units
+	MPG,
+	MPH,
+
+	// Mathematics
 	Pi,
 	Phi,
-	E
+	E,
 }
 
 impl Constant {
 	pub fn to_string(&self) -> String {
 		match self {
+			// Fake units
+			Constant::MPG => { String::from("mpg") },
+			Constant::MPH => { String::from("mph") },
+
+			// Mathematics
 			Constant::Pi => { String::from("π") },
 			Constant::Phi => { String::from("φ") },
-			Constant::E => { String::from("e") },
+			Constant::E => { String::from("e") }
 		}
 	}
 }