add help

src/main.rs

@@ -5,16 +5,14 @@ mod compiler;
 mod context;
 mod vm;
 
-use std::{
-    env,
-    fs::read_to_string,
-};
+use std::{ env, fs::read_to_string, };
 use err::*;
 use parser::*;
 use compiler::*;
 use context::*;
 use vm::*;
 
+const VERSION: &str = env!("CARGO_PKG_VERSION");
 
 // https://playsecurity.org/rawfile/grass_mud_horse_language_specification.md
 // https://p.rogram.me/grassmudhorse.js/grassmudhorse.js
@@ -24,8 +22,16 @@ fn main() {
     let is_compile = env::args().any(|a| a == "-c" || a == "--compile");
     let arg_file = env::args().filter(|a| !a.starts_with("-")).nth(1);
 
+    if is_debug {
+        println!("[DEBUG] Run in debug mode");
+    }
+
     if is_help {
-        println!("grassmudhorse.rs v0.1");
+        println!("GrassMudHorse in Rust v{}\n", VERSION);
+        println!("grassmudhorse [OPTIONS] file_name");
+        println!("  -h, --help     print this message");
+        println!("  -d, --debug    run in debug mode");
+        println!("  -c, --compile  compile grassmudhorse source code");
         return;
     }
 
@@ -51,14 +57,14 @@ fn main() {
     if is_compile {
         match compile_lang(&input) {
             Ok(compiled) => println!("{}", compiled),
-            Err(err) => println!("Compile error: {}", err),
+            Err(err) => println!("[ERROR] Compile error: {}", err),
         }
         return;
     }
 
     let instructions = match parse_lang(&input) {
         Ok(i) => i, Err(err) => {
-            println!("Parse error: {}", err);
+            println!("[ERROR] Parse error: {}", err);
             return;
         },
     };
@@ -77,7 +83,7 @@ fn main() {
 
     match vm.execute(&mut context) {
         Err(RuntimeError::EndVm) => (),
-        Err(err) => println!("Vm error: {}", err),
+        Err(err) => println!("[ERROR] Vm error: {}", err),
         Ok(_) => (),
     }