Implement interpret from file resolves #6

src/main.rs

@@ -3,6 +3,10 @@ mod interpreter;
 mod lexer;
 mod parser;
 mod primitives;
+
+use std::path::Path;
+use std::fs;
+use std::env;
 use std::io;
 use std::io::prelude::*;
 
@@ -32,14 +36,29 @@ fn interpret_code(scm_code: &str) {
     println!("{:?}", result);
 }
 
-fn interpret_file() {}
+fn interpret_file(filename: &Path) {
+    match fs::read_to_string(filename) {
+        Ok(scm_code) => {
+            let tokens = lexer::read(scm_code.as_str());
+            let datum = parser::parse(tokens);
+            let mut env = environment::get_global_environment();
+            let result = interpreter::interpret(&datum, &mut env);
+            println!("{:?}", result);
+        },
+        Err(error) => println!("error: {} {:?}", error, filename),
+    }
+}
 
 fn main() {
+    let args: Vec<String> = env::args().collect();
     // let scm_code = "(begin (define (f n) (if (= n 1) 1 (* n (f (- n 1))))) (f 10))";
     let scm_code = "";
 
     if scm_code.len() > 0 {
         interpret_code(scm_code);
+    } else if args.len() == 2 {
+        let arg_path = Path::new(&args[1]);
+        interpret_file(arg_path);
     } else {
         repl();
     }