print periodic table when no args are supplied

src/main.rs

@@ -7,7 +7,7 @@ mod variations;
 use std::env;
 use parse::parse;
 
-use periodic_table::Element;
+use periodic_table::{Element, periodic_table};
 
 use crate::variations::calculate::get_variations;
 
@@ -25,6 +25,11 @@ fn main() {
         args.push(argument);
     }
     
+    if args.len() < 2 {
+        println!("{:#?}", periodic_table());
+        return
+    }
+
     let elements = parse(&args[1]);
     println!("{:#?}", elements);
     println!("{}", elements.len());