catching uncatched Throw

Author: mmatera

mathics/builtin/control.py

@@ -788,7 +788,8 @@ class Throw(Builtin):
       = ...
      << Catch[NestList[If[# > 1000, Throw[#], #^2 + 1] &, 1, 7]]
       = 458330
-
+     << Throw[1]
+      = Null
     """
     messages = {'nocatch': 'Uncaught `1` returned to top level.', }
 

mathics/core/evaluation.py

@@ -336,6 +336,19 @@ def evaluate():
                     self.exc_result = Expression("Overflow")
                 else:
                     raise
+            except WLThrowInterrupt as ti:
+                print("query: ", query)
+                if ti.tag:
+                    self.exc_result = Expression("Hold",
+                                                 Expression("Throw",
+                                                            ti.value,
+                                                            ti.tag))
+                else:
+                    self.exc_result = Expression("Hold",
+                                                 Expression("Throw",
+                                                            ti.value
+                                                            ))
+                self.message("Throw", "nocatch", self.exc_result)
             except OverflowError:
                 self.message("General", "ovfl")
                 self.exc_result = Expression("Overflow")