4 files changed, 47 insertions, 4 deletions
diff --git a/rust/src/lambda.rs b/rust/src/lambda.rs
index 97b6f08..416c31e 100644
--- a/rust/src/lambda.rs
+++ b/rust/src/lambda.rs
@@ -1,5 +1,9 @@
 use rand::Rng;
-use std::{collections::HashMap, fs::read_to_string};
+use std::{
+    collections::HashMap,
+    fs::read_to_string,
+    io::{BufRead, BufReader, Read, Write},
+};
 
 mod ast;
 use ast::*;
@@ -58,6 +62,33 @@ pub fn eval_file(file_name: &str) -> String {
         .join(" ")
 }
 
+pub fn repl<I: Read, O: Write>(inp: &mut I, outp: &mut O) {
+    let mut env = Environment::new();
+    let mut reader = BufReader::new(inp);
+    loop {
+        let mut input = String::new();
+        write!(outp, "> ").unwrap();
+        outp.flush().unwrap();
+        match reader.read_line(&mut input) {
+            Ok(0) => break,
+            Ok(_) => (),
+            Err(e) => {
+                writeln!(outp, "{}", e).unwrap();
+                break;
+            }
+        }
+        let values = parse(&input);
+        let results = values
+            .iter()
+            .map(|v| eval(v, &mut env))
+            .collect::<Vec<Value>>();
+        for result in results {
+            writeln!(outp, "{}", result).unwrap();
+            outp.flush().unwrap();
+        }
+    }
+}
+
 fn eval_all(values: &[Value]) -> Vec<Value> {
     let mut env = Environment::new();
     values.iter().map(|v| eval(v, &mut env)).collect()
diff --git a/rust/src/main.rs b/rust/src/main.rs
index ffd92f2..136e868 100644
--- a/rust/src/main.rs
+++ b/rust/src/main.rs
@@ -1,11 +1,16 @@
-use std::env::args;
+use std::{
+    env::args,
+    io::{stdin, stdout},
+};
 
-use lambda::eval_file;
+use lambda::{eval_file, repl};
 
 fn main() {
     if args().count() > 1 {
         for file in args().skip(1) {
             println!("{}", eval_file(&file));
         }
+    } else {
+        repl(&mut stdin(), &mut stdout());
     }
 }
diff --git a/rust/src/parser.rs b/rust/src/parser.rs
index b065ec3..23a512b 100644
--- a/rust/src/parser.rs
+++ b/rust/src/parser.rs
@@ -76,7 +76,6 @@ fn parse_definition(parser: &mut Parser) -> Result<Value, String> {
         parser.backtrack();
         e.to_string()
     })?;
-    println!("parser {:?}", parser);
     let var = parse_variable(parser)?;
     let body = parse_expression(parser)?;
     parser.expect(Token::RParen)?;
diff --git a/rust/tests/interpret_test.rs b/rust/tests/interpret_test.rs
index 61b0712..40c3ee5 100644
--- a/rust/tests/interpret_test.rs
+++ b/rust/tests/interpret_test.rs
@@ -7,3 +7,11 @@ fn interpreter_can_read_and_interpret_file() {
     assert_eq!("1", eval_file("sample/test_normal.txt"));
     assert_eq!("13", eval_file("sample/test_let.txt"));
 }
+
+#[test]
+fn repl_can_read_and_interpret_input() {
+    let input = "(def id (lam x x))\n(id 12)";
+    let mut output = Vec::new();
+    lambda::repl(&mut input.as_bytes(), &mut output);
+    assert_eq!("> true\n> 12\n> ", String::from_utf8(output).unwrap());
+}