Add interpretation logging controlled by FUNSOR_DEBUG=1 (#93)

* Add interpretation logging controlled by FUNSOR_DEBUG

* Simplify debug printing

* Improve pretty printing of Stack and Joint

funsor/interpreter.py

@@ -1,5 +1,6 @@
 from __future__ import absolute_import, division, print_function
 
+import os
 import types
 from collections import OrderedDict
 
@@ -11,11 +12,28 @@
 from funsor.registry import KeyedRegistry
 from funsor.six import singledispatch
 
+_DEBUG = int(os.environ.get("FUNSOR_DEBUG", 0))
+_STACK_SIZE = 0
+
 _INTERPRETATION = None  # To be set later in funsor.terms
 
 
-def interpret(cls, *args):
-    return _INTERPRETATION(cls, *args)
+if _DEBUG:
+    def interpret(cls, *args):
+        global _STACK_SIZE
+        indent = '  ' * _STACK_SIZE
+        typenames = [cls.__name__] + [type(arg).__name__ for arg in args]
+        print(indent + ' '.join(typenames))
+        _STACK_SIZE += 1
+        try:
+            result = _INTERPRETATION(cls, *args)
+        finally:
+            _STACK_SIZE -= 1
+        print(indent + '-> ' + type(result).__name__)
+        return result
+else:
+    def interpret(cls, *args):
+        return _INTERPRETATION(cls, *args)
 
 
 def set_interpretation(new):

funsor/terms.py

@@ -150,6 +150,10 @@ def _pretty(self, lines, indent=0):
         for arg in self._ast_values:
             if isinstance(arg, Funsor):
                 arg._pretty(lines, indent + 1)
+            elif type(arg) is tuple and all(isinstance(x, Funsor) for x in arg):
+                lines.append((indent + 1, 'tuple'))
+                for x in arg:
+                    x._pretty(lines, indent + 2)
             else:
                 lines.append((indent + 1, str(arg)))