bug fixes and performance improvements

src/interpreter/error.rs

@@ -0,0 +1,27 @@
+use std::fmt::Display;
+use std::rc::Rc;
+
+use crate::representations::interpreted::ExprInst;
+use crate::foreign::ExternError;
+
+/// Problems in the process of execution
+#[derive(Clone)]
+pub enum RuntimeError {
+  Extern(Rc<dyn ExternError>),
+  NonFunctionApplication(ExprInst),
+}
+
+impl From<Rc<dyn ExternError>> for RuntimeError {
+  fn from(value: Rc<dyn ExternError>) -> Self {
+    Self::Extern(value)
+  }
+}
+
+impl Display for RuntimeError {
+  fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+    match self {
+      Self::Extern(e) => write!(f, "Error in external function: {e}"),
+      Self::NonFunctionApplication(loc) => write!(f, "Primitive applied as function at {loc:?}")
+    }
+  }
+}