Introduce basic REPL

1 files changed, 32 insertions, 1 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()