Add events, event history, and transition history to runtime interface

README.md

@@ -1,5 +1,5 @@
 
-# Frame Language Transpiler v0.7.0
+# Frame Language Transpiler v0.7.1
 
 
 Hi! So very glad you are interested in Frame. Frame system design markdown language for software architects and engineers. It is an easy to learn textual language for defining system specifications that can generate both UML documentation as well as code in 7 langauges. 

frame_runtime/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "frame_runtime"
-version = "0.7.0"
+version = "0.7.1"
 authors = ["Eric Walkingshaw <eric.walkingshaw@savant.com>"]
 edition = "2018"
 
@@ -9,3 +9,7 @@ edition = "2018"
 crate-type = ["rlib"]
 
 [dependencies]
+once_cell = "1.8.0"
+
+[dev-dependencies]
+indoc = "1.0.3"

frame_runtime/src/env.rs

@@ -2,6 +2,8 @@
 //! name bindings.
 
 use std::any::Any;
+use std::cell::{Ref, RefCell};
+use std::rc::Rc;
 
 /// Environments associate names (i.e. variables/parameters) with values.
 ///
@@ -12,7 +14,7 @@ use std::any::Any;
 /// It is common for a particular environment to be absent because there are no variables of the
 /// kind held by that environment. We represent absent environments by an empty environment rather
 /// than using an `Option` type because it simplifies the interface and because the distinction
-/// between `None` and `Some(EMPTY)` is not significant.
+/// between `None` and `Some(empty)` is not significant.
 pub trait Environment {
     /// Is this the empty environment?
     fn is_empty(&self) -> bool {
@@ -22,13 +24,30 @@ pub trait Environment {
     fn lookup(&self, name: &str) -> Option<&dyn Any>;
 }
 
-/// The trivial empty environment. This can be used in place of an environment when that
-/// environment is absent.
-pub const EMPTY: &'static dyn Environment = &EmptyEnvironment {};
+/// The trivial empty enviorment. This can be used in place of an environment when that environment
+/// is absent.
+#[derive(Clone, Debug, Eq, Hash, PartialEq, PartialOrd, Ord)]
+pub struct Empty {}
 
-struct EmptyEnvironment {}
+impl Empty {
+    /// Create a new empty environment.
+    pub fn new() -> Empty {
+        Empty {}
+    }
 
-impl Environment for EmptyEnvironment {
+    /// Create a new reference-counted pointer to an empty environment.
+    pub fn new_rc() -> Rc<Empty> {
+        Rc::new(Empty::new())
+    }
+}
+
+impl Default for Empty {
+    fn default() -> Self {
+        Empty::new()
+    }
+}
+
+impl Environment for Empty {
     fn is_empty(&self) -> bool {
         true
     }
@@ -37,6 +56,24 @@ impl Environment for EmptyEnvironment {
     }
 }
 
+impl<'a, T: Environment> Environment for Ref<'a, T> {
+    fn is_empty(&self) -> bool {
+        (**self).is_empty()
+    }
+    fn lookup(&self, name: &str) -> Option<&dyn Any> {
+        (**self).lookup(name)
+    }
+}
+
+impl<T: Environment> Environment for RefCell<T> {
+    fn is_empty(&self) -> bool {
+        self.borrow().is_empty()
+    }
+    fn lookup(&self, name: &str) -> Option<&dyn Any> {
+        unsafe { (*self.as_ptr()).lookup(name) }
+    }
+}
+
 #[allow(clippy::approx_constant)]
 #[cfg(test)]
 mod tests {
@@ -61,14 +98,16 @@ mod tests {
 
     #[test]
     fn empty_environment_is_empty() {
-        assert!(EMPTY.is_empty());
+        let empty = Empty::new();
+        assert!(empty.is_empty());
     }
 
     #[test]
     fn empty_environment_returns_none() {
-        assert!(EMPTY.lookup("x").is_none());
-        assert!(EMPTY.lookup("y").is_none());
-        assert!(EMPTY.lookup("z").is_none());
+        let empty = Empty::new();
+        assert!(empty.lookup("x").is_none());
+        assert!(empty.lookup("y").is_none());
+        assert!(empty.lookup("z").is_none());
     }
 
     #[test]