Implement basic builtin functions

src/builtin/color.rs

@@ -0,0 +1,11 @@
+use std::collections::BTreeMap;
+
+use super::Builtin;
+use crate::value::Value;
+
+pub(crate) fn register(f: &mut BTreeMap<String, Builtin>) {
+    f.insert("rgb".to_owned(), Box::new(|args| {
+        let red = args.get("red");
+        todo!()
+    }));
+}

src/builtin/mod.rs

@@ -1,15 +1,20 @@
 use lazy_static::lazy_static;
 use std::collections::BTreeMap;
 
+use crate::args::CallArgs;
 use crate::common::Scope;
 use crate::function::Function;
 use crate::value::Value;
 
-pub(crate) type Builtin = dyn Fn(&Scope) -> Value + Send + Sync;
+mod color;
+
+pub(crate) type Builtin = Box<dyn Fn(&CallArgs) -> Value + Send + Sync>;
 
 lazy_static! {
-    pub(crate) static ref GLOBAL_FUNCTIONS: BTreeMap<String, Function> = {
-        let m = BTreeMap::new();
+    pub(crate) static ref GLOBAL_FUNCTIONS: BTreeMap<String, Builtin> = {
+        let mut m = BTreeMap::new();
+        color::register(&mut m);
         m
     };
 }
+

src/value.rs

@@ -279,7 +279,7 @@ impl Value {
                         let func = match scope.functions.get(&s) {
                             Some(f) => f,
                             None => match GLOBAL_FUNCTIONS.get(&s) {
-                                Some(f) => f,
+                                Some(f) => return Some(f(&args)),
                                 None => todo!("called undefined function"),
                             },
                         };