Added support for interpreter directives

src/main.rs

@@ -1,6 +1,7 @@
 use std::io;
 use std::io::Write;
 use std::io::BufRead;
+use std::process;
 
 use tokenizer::tokenize;
 use parser::{parse, ParseResult};
@@ -19,16 +20,22 @@ fn repl() {
     let mut stdout = io::stdout();
     let mut buf = String::with_capacity(20);
     loop {
+        buf.clear();
         print!(">> ");
         stdout.flush().ok();
         let line = stdin.lock().read_line(&mut buf);
+
         match line {
             Ok(_) => {
                 if buf.is_empty() {
                     break;
                 }
+
+                if handle_interpreter_directive(&buf) {
+                    continue;
+                }
+
                 let tokens = tokenize(&buf);
-                buf.clear();
                 println!("Tokens: {:?}", tokens);
 
                 match parse(tokens) {
@@ -47,3 +54,25 @@ fn repl() {
         }
     }
 }
+
+fn handle_interpreter_directive(input: &str) -> bool {
+
+    match input.chars().nth(0) {
+        Some('.') => (),
+        _ => return false
+    }
+
+    let commands: Vec<&str> = input.split(|c: char| c.is_whitespace()).collect();
+    match commands.get(0) {
+        Some(s) if *s == ".quit" => {
+            println!("Siturei simasu");
+            process::exit(0);
+        },
+        Some(s) => {
+            println!("Unknown directive: {}", s);
+        },
+        None => () //should never happen
+    }
+
+    return true;
+}