Merge pull request #1306 from mathics/toexpression-unaryop

fix support for \!

Author: mmatera

mathics/builtin/strings.py

@@ -14,7 +14,13 @@
 from typing import Any, Callable, List
 
 from mathics.version import __version__  # noqa used in loading to check consistency.
-from mathics.builtin.base import BinaryOperator, Builtin, Test, Predefined
+from mathics.builtin.base import (
+    BinaryOperator,
+    Builtin,
+    Test,
+    Predefined,
+    PrefixOperator,
+)
 from mathics.core.expression import (
     Expression,
     Symbol,
@@ -1878,6 +1884,31 @@ def apply_form(self, value, form, evaluation, options):
         return String(text)
 
 
+class InterpretedBox(PrefixOperator):
+    """
+    <dl>
+      <dt>'InterpretedBox[$box$]'
+      <dd>is the ad hoc fullform for \! $box$. just
+          for internal use...
+
+    >> \! \(2+2\)
+     = 4
+    </dl>
+    """
+
+    operator = "\\!"
+    precedence = 670
+
+    def apply_dummy(self, boxes, evaluation):
+        """InterpretedBox[boxes_]"""
+        # TODO: the following is a very raw and dummy way to
+        # handle these expressions.
+        # In the first place, this should handle different kind
+        # of boxes in different ways.
+        reinput = boxes.boxes_to_text()
+        return Expression("ToExpression", reinput).evaluate(evaluation)
+
+
 class ToExpression(Builtin):
     """
     <dl>
@@ -1926,7 +1957,6 @@ class ToExpression(Builtin):
     #> ToExpression["log(x)", StandardForm]
      = log x
     """
-
     attributes = ("Listable", "Protected")
 
     messages = {

mathics/core/expression.py

@@ -1513,6 +1513,8 @@ def boxes_to_text(self, **options) -> str:
             )
         elif self.has_form("SuperscriptBox", 2):
             return "^".join([leaf.boxes_to_text(**options) for leaf in self._leaves])
+        elif self.has_form("FractionBox", 2):
+            return "/".join([" ( " + leaf.boxes_to_text(**options)+ " ) " for leaf in self._leaves])
         else:
             raise BoxError(self, "text")
 

mathics/core/parser/operators.py

@@ -18,6 +18,7 @@
     "Not": 230,
     "Information": 5001,
     "Definition": 5000,
+    "InterpretedBox": 670,
 }
 
 postfix_ops = {

mathics/core/parser/parser.py

@@ -170,6 +170,8 @@ def parse_box(self, p):
             elif result is None and tag != "END":
                 self.consume()
                 new_result = String(token.text)
+                if new_result.value == r"\(":
+                    new_result = self.p_LeftRowBox(token)
             else:
                 new_result = None
             if new_result is None:
@@ -311,7 +313,8 @@ def p_LeftRowBox(self, token):
         self.bracket_depth += 1
         token = self.next()
         while token.tag not in ("RightRowBox", "OtherscriptBox"):
-            children.append(self.parse_box(0))
+            newnode = self.parse_box(0)
+            children.append(newnode)
             token = self.next()
         if len(children) == 0:
             result = String("")