input function

src/interp/mod.rs

@@ -65,6 +65,13 @@ impl Interpreter {
             receiver: None,
         }));
 
+        self.get_env_mut().def("input".to_string(), Value::Func(Func::Native {
+            name: "input".to_string(),
+            params: None,
+            func: input,
+            receiver: None,
+        }));
+
         self.get_env_mut().def("exit".to_string(), Value::Func(Func::Native {
             name: "exit".to_string(),
             params: Some(1),

src/interp/native.rs

@@ -1,5 +1,7 @@
 use std::cell::RefCell;
 use std::collections::HashMap;
+use std::io;
+use std::io::{BufRead, Write};
 use std::process;
 use std::rc::Rc;
 
@@ -25,6 +27,27 @@ pub fn print(int: &mut Interpreter, args: Vec<Value>) -> Value {
     Value::Nil
 }
 
+pub fn input(int: &mut Interpreter, mut args: Vec<Value>) -> Value {
+    if int.collector.is_some() {
+        panic!("called input in testing");
+    }
+
+    let msg = match args.remove(0) {
+        Value::String(msg) => msg,
+        _ => panic!("expected arg to be string")
+    };
+
+    print!("{}", msg);
+    io::stdout().flush().unwrap();
+
+    let mut buf = String::new();
+
+    let stdin = io::stdin();
+    stdin.lock().read_line(&mut buf).unwrap();
+
+    Value::String(buf)
+}
+
 pub fn exit(_: &mut Interpreter, mut args: Vec<Value>) -> Value {
     let code = match args.remove(0) {
         Value::Num(num) if num.trunc() == num => num as i32,

src/interp/test.rs

@@ -1,9 +1,10 @@
+use std::fs;
+
 use crate::lexer::new as new_lexer;
 use crate::parser::Parser;
 
 use super::*;
 use super::value::Value;
-use std::fs;
 
 fn output(source: &str) -> String {
     let lexer = new_lexer(source.to_owned());