Implement list type

examples/program10.graphol

@@ -0,0 +1,19 @@
+// Composition examples: pass list to blocks and mutate nested lists.
+
+show_list {
+    data inbox
+    echo ("received -> " data)
+    echo ("first item -> " (list_get data 0))
+    echo ("len -> " (list_len data))
+}
+
+payload (list "graph" "oriented" "language")
+show_list payload run
+
+mixed (list 1 "two" true (list 3 4))
+echo ("mixed -> " mixed)
+echo ("nested before push -> " (list_get mixed 3))
+
+list_push (list_get mixed 3) 5
+echo ("nested after push -> " (list_get mixed 3))
+echo ("mixed after nested push -> " mixed)

examples/program8.graphol

@@ -0,0 +1,18 @@
+// List basics: create, push, get, set, pop, len.
+
+nums (list 1 2 3)
+echo ("initial -> " nums)
+
+list_push nums 4
+echo ("after push -> " nums)
+echo ("len -> " (list_len nums))
+
+echo ("index 0 -> " (list_get nums 0))
+echo ("index 2 -> " (list_get nums 2))
+
+list_set nums 1 99
+echo ("after set index 1 -> " nums)
+
+last (list_pop nums)
+echo ("popped -> " last)
+echo ("after pop -> " nums)

examples/program9.graphol

@@ -0,0 +1,18 @@
+// Safe edge cases: empty pop, out-of-range get/set.
+
+empty (list)
+echo ("empty len -> " (list_len empty))
+
+if (list_pop empty) {
+    echo "unexpected"
+} else {
+    echo "pop on empty returns null (falsy)"
+}
+
+nums (list 10 20)
+echo ("before invalid operations -> " nums)
+
+echo ("out-of-range get (index 9) -> " (list_get nums 9))
+list_set nums 9 777
+
+echo ("after invalid set (should be unchanged) -> " nums)

src/compiler/codegen.rs

@@ -9,6 +9,8 @@ const IO_SOURCE: &str = include_str!("../runtime/io.rs");
 const VALUE_SOURCE: &str = include_str!("../runtime/value.rs");
 const OBJECT_SOURCE: &str = include_str!("../runtime/object.rs");
 const OBJECT_COMMANDS_SOURCE: &str = include_str!("../runtime/object/object_commands.rs");
+const LIST_OBJECT_SOURCE: &str = include_str!("../runtime/object/list_object.rs");
+const LIST_COMMANDS_SOURCE: &str = include_str!("../runtime/object/list_commands.rs");
 const NODE_PRIMITIVES_SOURCE: &str =
     include_str!("../runtime/object/object_strategies/node_primitives.rs");
 const NUMERIC_OPS_SOURCE: &str = include_str!("../runtime/object/object_strategies/numeric_ops.rs");
@@ -60,6 +62,8 @@ fn runtime_module_source() -> String {
 
     out.push_str("    pub mod object {\n");
     push_nested_module(&mut out, "object_commands", OBJECT_COMMANDS_SOURCE, 2);
+    push_nested_module(&mut out, "list_object", LIST_OBJECT_SOURCE, 2);
+    push_nested_module(&mut out, "list_commands", LIST_COMMANDS_SOURCE, 2);
 
     out.push_str("        mod object_strategies {\n");
     out.push_str("            mod strategy_core {\n");
@@ -120,7 +124,10 @@ fn strip_object_module_decls(source: &str) -> String {
         .lines()
         .filter(|line| {
             let trimmed = line.trim();
-            trimmed != "mod object_commands;" && trimmed != "mod object_strategies;"
+            trimmed != "mod object_commands;"
+                && trimmed != "mod list_object;"
+                && trimmed != "mod list_commands;"
+                && trimmed != "mod object_strategies;"
         })
         .collect::<Vec<_>>()
         .join("\n")

src/runtime/executor.rs

@@ -6,7 +6,7 @@ use super::host::ExecutionHost;
 use super::io::{OutputEvent, OutputMode, RuntimeIo};
 use super::object::{
     BlockSnapshot, StdoutState, end_object, new_block, new_boolean_operator, new_logic_operator,
-    new_node, new_operator, receive_object,
+    new_list, new_node, new_operator, receive_object,
 };
 use super::scope::{Scope, ScopeRef};
 use super::value::{ObjectRef, Value};
@@ -265,6 +265,10 @@ impl RuntimeEngine {
     fn eval_root(&mut self, node: &NodeExpr, scope: &ScopeRef) -> Result<ObjectRef, RuntimeError> {
         match node {
             NodeExpr::Identifier(name) => {
+                if name == "list" {
+                    return Ok(new_list());
+                }
+
                 if let Some(literal) = parse_literal(name) {
                     let node_ref = new_node();
                     receive_object(&node_ref, literal, self);
@@ -292,7 +296,11 @@ impl RuntimeEngine {
     fn eval_message(&mut self, node: &NodeExpr, scope: &ScopeRef) -> Result<Value, RuntimeError> {
         let value = match node {
             NodeExpr::Identifier(name) => {
-                parse_literal(name).unwrap_or_else(|| Value::Obj(Scope::get(scope, name)))
+                if name == "list" {
+                    Value::Obj(new_list())
+                } else {
+                    parse_literal(name).unwrap_or_else(|| Value::Obj(Scope::get(scope, name)))
+                }
             }
             NodeExpr::StringLiteral(text) => Value::Text(text.clone()),
             NodeExpr::Reserved(token) => Value::Obj(reserved_to_object(*token)?),

src/runtime/object.rs

@@ -1,4 +1,6 @@
 mod object_commands;
+mod list_commands;
+mod list_object;
 mod object_strategies;
 
 use std::any::Any;
@@ -16,6 +18,8 @@ pub use object_commands::{
     new_block, new_echo, new_if, new_input, new_message_async, new_message_else, new_message_run,
     new_stdout, new_while,
 };
+pub use list_commands::{new_list_get, new_list_len, new_list_pop, new_list_push, new_list_set};
+pub use list_object::new_list;
 pub use object_strategies::{
     new_boolean_operator, new_logic_operator, new_node, new_number, new_operator, new_string,
 };
@@ -71,6 +75,26 @@ pub trait GrapholObject {
         None
     }
 
+    fn list_len(&self) -> Option<usize> {
+        None
+    }
+
+    fn list_get(&self, _index: usize) -> Option<Value> {
+        None
+    }
+
+    fn list_set(&mut self, _index: usize, _value: Value) -> bool {
+        false
+    }
+
+    fn list_pop(&mut self) -> Option<Value> {
+        None
+    }
+
+    fn list_push(&mut self, _value: Value) -> bool {
+        false
+    }
+
     fn as_any(&self) -> &dyn Any;
 }