Have the repl loop

cli/src/repl.rs

@@ -38,26 +38,38 @@ pub fn main() -> io::Result<()> {
     use std::io::BufRead;
 
     println!(
-        "\n  The rockin’ \u{001b}[36mroc repl\u{001b}[0m\n\u{001b}[35m────────────────────────\n"
+        "\n  The rockin’ \u{001b}[36mroc repl\u{001b}[0m\n\u{001b}[35m────────────────────────\u{001b}[0m\n\nEnter :help for help, or :exit to exit."
     );
 
     // Loop
 
-    print!("\u{001b}[36m▶\u{001b}[0m ");
+    loop {
+        print!("\n\u{001b}[36m▶\u{001b}[0m ");
 
-    io::stdout().flush().unwrap();
+        io::stdout().flush().unwrap();
 
-    let stdin = io::stdin();
+        let stdin = io::stdin();
-    let line = stdin
+        let line = stdin
-        .lock()
+            .lock()
-        .lines()
+            .lines()
-        .next()
+            .next()
-        .expect("there was no next line")
+            .expect("there was no next line")
-        .expect("the line could not be read");
+            .expect("the line could not be read");
 
-    let (answer, answer_type) = gen(line.as_str(), Triple::host(), OptLevel::Normal);
+        match line.trim() {
+            ":help" => {
+                println!("Use :exit to exit.");
+            }
+            ":exit" => {
+                break;
+            }
+            line => {
+                let (answer, answer_type) = gen(line, Triple::host(), OptLevel::Normal);
 
-    println!("\n{} \u{001b}[35m:\u{001b}[0m {}", answer, answer_type);
+                println!("\n{} \u{001b}[35m:\u{001b}[0m {}", answer, answer_type);
+            }
+        }
+    }
 
     Ok(())
 }