Add tag to Dynamic.

src/packages/lang_core.rs

@@ -0,0 +1,45 @@
+use crate::def_package;
+use crate::dynamic::Tag;
+use crate::plugin::*;
+use crate::{Dynamic, EvalAltResult, INT};
+#[cfg(feature = "no_std")]
+use std::prelude::v1::*;
+
+#[export_module]
+mod core_functions {
+    #[rhai_fn(name = "tag", get = "tag", pure)]
+    pub fn get_tag(value: &mut Dynamic) -> INT {
+        value.tag() as INT
+    }
+    #[rhai_fn(name = "set_tag", set = "tag", return_raw)]
+    pub fn set_tag(value: &mut Dynamic, tag: INT) -> Result<(), Box<EvalAltResult>> {
+        if tag < Tag::MIN as INT {
+            Err(Box::new(EvalAltResult::ErrorArithmetic(
+                format!(
+                    "{} is too small to fit into a tag (must be between {} and {})",
+                    tag,
+                    Tag::MIN,
+                    Tag::MAX
+                ),
+                Position::NONE,
+            )))
+        } else if tag > Tag::MAX as INT {
+            Err(Box::new(EvalAltResult::ErrorArithmetic(
+                format!(
+                    "{} is too large to fit into a tag (must be between {} and {})",
+                    tag,
+                    Tag::MIN,
+                    Tag::MAX
+                ),
+                Position::NONE,
+            )))
+        } else {
+            value.set_tag(tag as Tag);
+            Ok(())
+        }
+    }
+}
+
+def_package!(crate:LanguageCorePackage:"Language core functions.", lib, {
+    combine_with_exported_module!(lib, "language_core", core_functions);
+});