fix Infix grouping

Author: mmatera

mathics/builtin/makeboxes.py

@@ -18,14 +18,23 @@
 from mathics.core.list import ListExpression
 from mathics.core.number import dps
 from mathics.core.symbols import Atom, Symbol
-from mathics.core.systemsymbols import SymbolInputForm, SymbolOutputForm, SymbolRowBox
+from mathics.core.systemsymbols import (
+    SymbolInputForm,
+    SymbolLeft,
+    SymbolNone,
+    SymbolOutputForm,
+    SymbolRight,
+    SymbolRowBox,
+)
 from mathics.eval.makeboxes import (
     NEVER_ADD_PARENTHESIS,
     _boxed_string,
     format_element,
     parenthesize,
 )
 
+SymbolNonAssociative = Symbol("System`NonAssociative")
+
 
 def int_to_s_exp(expr, n):
     n = expr.get_int_value()
@@ -39,18 +48,26 @@ def int_to_s_exp(expr, n):
     return s, exp, nonnegative
 
 
-def make_boxes_infix(elements, op: String, precedence: int, grouping, form: Symbol):
+def make_boxes_infix(elements, op: String, precedence: int, form: Symbol):
     result = []
+    last_indx = len(elements) - 1
     for index, element in enumerate(elements):
-        if index > 0:
-            result.append(op)
+        grouping = SymbolNone
+        if element.has_form("Infix", 4):
+            grouping = element.elements[-1]
+
+            # if grouping  not in (SymbolNone, SymbolLeft,SymbolRight,SymbolNonAssociative):
+            #      send message
+
         parenthesized = False
-        if grouping == "System`NonAssociative":
-            parenthesized = True
-        elif grouping == "System`Left" and index > 0:
-            parenthesized = True
-        elif grouping == "System`Right" and index == 0:
-            parenthesized = True
+        if index == 0:
+            parenthesized = grouping in (SymbolRight, SymbolNonAssociative)
+        elif index == last_indx:
+            result.append(op)
+            parenthesized = grouping in (SymbolLeft, SymbolNonAssociative)
+        else:
+            result.append(op)
+            parenthesized = grouping is (SymbolLeft, SymbolRight, SymbolNonAssociative)
 
         element_boxes = MakeBoxes(element, form)
         element = parenthesize(precedence, element, element_boxes, parenthesized)
@@ -462,7 +479,6 @@ def format_operator(operator) -> Union[String, BaseElement]:
         py_precedence = (
             precedence.value if hasattr(precedence, "value") else NEVER_ADD_PARENTHESIS
         )
-        grouping = grouping.get_name()
 
         if isinstance(expr, Atom):
             evaluation.message("Infix", "normal", Integer1)
@@ -484,7 +500,7 @@ def format_operator(operator) -> Union[String, BaseElement]:
                     String(operator_to_unicode.get(op_str, op_str))
                 )
 
-            return make_boxes_infix(elements, operator, py_precedence, grouping, form)
+            return make_boxes_infix(elements, operator, py_precedence, form)
 
         elif len(elements) == 1:
             return MakeBoxes(elements[0], form)