+-- Can the given core expression be applied to something? This is true for
+-- applying to a value as well as a type.
+is_applicable :: CoreSyn.CoreExpr -> Bool
+is_applicable expr = is_fun expr || is_poly expr
+
+-- Is the given core expression a variable or an application?
+is_simple :: CoreSyn.CoreExpr -> Bool
+is_simple (CoreSyn.App _ _) = True
+is_simple (CoreSyn.Var _) = True
+is_simple (CoreSyn.Cast expr _) = is_simple expr
+is_simple _ = False
+