diff --git a/tools/python/jwutils/algo/ShuntingYard.py b/tools/python/jwutils/algo/ShuntingYard.py
index dc20e6e..f2c23d9 100644
--- a/tools/python/jwutils/algo/ShuntingYard.py
+++ b/tools/python/jwutils/algo/ShuntingYard.py
@@ -171,11 +171,12 @@ class ShuntingYard(object): # export
             table.append( (v, action, outq, (s[0] for s in stack), note) )
             v = note = ''
         if self.do_debug:
-            maxcolwidths = [len(max(x, key=len)) for x in zip(*table)]
+            maxcolwidths = [len(max(x, key=len)) for x in [zip(*table)]]
+            caller = get_caller_pos()
             row = table[0]
-            print(' '.join('{cell:^{width}}'.format(width=width, cell=cell) for (width, cell) in zip(maxcolwidths, row)))
+            slog(DEBUG, ' '.join('{cell:^{width}}'.format(width=width, cell=cell) for (width, cell) in zip(maxcolwidths, row)))
             for row in table[1:]:
-                print(' '.join('{cell:<{width}}'.format(width=width, cell=cell) for (width, cell) in zip(maxcolwidths, row)))
+                slog(DEBUG, ' '.join('{cell:<{width}}'.format(width=width, cell=cell) for (width, cell) in zip(maxcolwidths, row)))
         return table[-1][2]
 
     def infix_to_postfix_orig(self, infix):