input function

src/stl/strings.rs

@@ -17,6 +17,8 @@
 
 use crate::segment::{Ctr, Seg};
 use crate::sym::SymTable;
+use std::io::Write;
+use std::io;
 
 pub const ECHO_DOCSTRING: &str =
     "traverses any number of arguments. Prints their evaluated values on a new line for each.";
@@ -150,3 +152,19 @@ pub fn split_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
 
     Ok(Ctr::Seg(ret))
 }
+
+pub const INPUT_DOCSTRING: &str = "Takes one argument (string) and prints it.
+Then prompts for user input.
+User input is returned as a string";
+
+pub fn input_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
+    if let Ctr::String(ref s) = *ast.car {
+        print!("{}", s);
+        let _= io::stdout().flush();
+        let mut input = String::new();
+        io::stdin().read_line(&mut input).expect("couldnt read user input");
+        Ok(Ctr::String(input.trim().to_string()))
+    } else {
+        Err("impossible: arg not string".to_string())
+    }
+}