Added help.

kalk_cli/src/main.rs

@@ -21,7 +21,20 @@ fn main() {
             break;
         };
 
-        if arg == "-i" {
+        match arg.as_ref() {
+            "-h" | "--help" => {
+                // The indentation... Will have to do something more scalable in the future.
+                println!(
+                    "
+-= kalk help =-\n
+kalk [OPTIONS] [INPUT]
+-h, --help : show this
+-i         : load a file with predefined functions/variables
+                "
+                );
+                return;
+            }
+            "-i" => {
                 let file_name = &args.next().expect("Expected input file."); // The next argument will be the file name.
                 let mut file_content = String::new();
                 File::open(&file_name)
@@ -33,12 +46,14 @@ fn main() {
                 // Output is not needed here.
                 parser::eval(&mut parser_context, &file_content, 53)
                     .expect("Failed to parse input file.");
-        } else {
+            }
+            _ => {
                 // Main argument. This is expected to be a maths expression.
                 // After the loop is finished, this will be parsed and outputted.
                 expr_input = Some(arg);
             }
         }
+    }
 
     if let Some(input) = expr_input {
         // Direct output