Add descriptions to commands and improve REPL display formatting

engine/src/core/repl/commands.rs

@@ -0,0 +1,36 @@
+use super::COMMAND_LIST;
+use std::process::Command;
+use log2::{debug, info};
+
+pub(crate) fn say_hello() {
+    println!("Hello, World!");
+}
+
+pub(crate) fn echo(args: Vec<String>) {
+    debug!("{}", args.join(" "));
+    println!("{}", args.join(" "))
+}
+
+pub(crate) fn exit() {
+    debug!("Exiting...");
+    std::process::exit(0)
+}
+
+pub(crate) fn clear() {
+    info!("Clearing screen..., running command");
+    let _result = if cfg!(target_os = "windows") {
+        debug!("target_os is windows");
+        Command::new("cmd").args(["/c", "cls"]).spawn()
+    } else {
+        debug!("target_os is unix");
+        // "clear" or "tput reset"
+        Command::new("tput").arg("reset").spawn()
+    };
+}
+
+pub(crate) fn help() {
+    println!("Commands:");
+    for cmd in COMMAND_LIST.commands.read().iter() {
+        println!("{:#}", cmd);
+    }
+}