add echo function

Signed-off-by: Ava Hahn <ava@aidanis.online>

src/lex.rs

@@ -28,14 +28,8 @@ pub fn lex(document: &String) -> Result<Box<Seg>, String> {
         return Err("document may only contain ascii characters".to_string());
     }
 
-    let mut document_normal = document.clone();
-    if !document_normal.ends_with(')') {
-        document_normal = document_normal + ")";
-    }
-    if !document_normal.starts_with('(') {
-        document_normal = "(".to_string() + &document_normal;
-    }
-
+    // finish a singlet token, or do nothing
+    let document_normal = document.clone() + " ";
     let tree = process(&document_normal);
 
     // TODO: Make multiple forms of Ok()
@@ -159,7 +153,11 @@ fn process(document: &String) -> Result<Box<Seg>, String> {
                 return Err("Empty token".to_string());
             }
 
-            let mut current_seg = ref_stack.pop().unwrap();
+            let mut return_singlet = false;
+            let mut current_seg = ref_stack.pop().unwrap_or_else(|| {
+                return_singlet = true;
+                Seg::new()
+            });
             let obj;
             if is_str {
                 obj = Box::from(Ctr::String(token));
@@ -185,7 +183,7 @@ fn process(document: &String) -> Result<Box<Seg>, String> {
                 current_seg.append(obj.clone());
             }
 
-            if alloc_list {
+            if alloc_list || return_singlet {
                 // return if we have finished the document
                 if ref_stack.is_empty() {
                     return Ok(Box::new(current_seg));

src/stl.rs

@@ -49,6 +49,16 @@ pub fn static_stdlib(syms: &mut SymTable) -> Result<(), String> {
         },
     );
 
+    syms.insert(
+        "echo".to_string(),
+        Symbol {
+            name: String::from("echo"),
+            args: Args::Infinite,
+            conditional_branches: false,
+            value: ValueType::Internal(Rc::new(_echo_callback)),
+        },
+    );
+
     syms.insert(
         "if".to_string(),
         Symbol {
@@ -90,6 +100,16 @@ pub fn dynamic_stdlib(syms: &mut SymTable) -> Result<(), String> {
     Ok(())
 }
 
+fn _echo_callback(ast: &Seg, _syms: &mut SymTable) -> Result<Ctr, String> {
+    if ast.len() == 1 {
+        println!("{}", ast.car);
+    } else {
+        ast.circuit(&mut |arg: &Ctr| print!("{}", arg) == ());
+    }
+
+    Ok(Ctr::None)
+}
+
 fn _store_callback(ast: &Seg, syms: &mut SymTable, env_cfg: bool) -> Result<Ctr, String> {
     let is_var = ast.len() == 2;
     if let Ctr::Symbol(ref identifier) = *ast.car {