Miscellaneous small evaluation improvements..

mathics/builtin/arithmetic.py

@@ -631,14 +631,23 @@ class I_(Predefined, SympyObject):
     summary_text = "imaginary unit number Sqrt[-1]"
     python_equivalent = 1j
 
+    def evaluate(self, evaluation: Evaluation):
+        return Complex(Integer0, Integer1)
+
     def is_constant(self) -> bool:
+        """The value and evaluation of this object can never change."""
         return True
 
-    def to_sympy(self, symb, **kwargs):
-        return self.sympy_obj
+    @property
+    def is_literal(self):
+        return True
 
-    def evaluate(self, evaluation: Evaluation):
-        return Complex(Integer0, Integer1)
+    @property
+    def value(self) -> complex:
+        return complex(0, 1)
+
+    def to_sympy(self, expr, **kwargs):
+        return self.sympy_obj
 
 
 class Im(SympyFunction):

mathics/builtin/numbers/constants.py

@@ -81,6 +81,7 @@ def eval_N(self, precision, evaluation):
         return self.get_constant(precision, evaluation)
 
     def is_constant(self) -> bool:
+        """The value and evaluation of this object can never change."""
         return True
 
     def get_constant(

mathics/builtin/tensors.py

@@ -18,7 +18,6 @@
 of any rank can be handled.
 """
 
-
 from mathics.core.atoms import Integer
 from mathics.core.attributes import A_FLAT, A_ONE_IDENTITY, A_PROTECTED
 from mathics.core.builtin import Builtin, InfixOperator
@@ -28,6 +27,7 @@
     eval_Inner,
     eval_LeviCivitaTensor,
     eval_Outer,
+    eval_Transpose2D,
     get_dimensions,
 )
 
@@ -378,15 +378,7 @@ class Transpose(Builtin):
 
     def eval(self, m, evaluation: Evaluation):
         "Transpose[m_?MatrixQ]"
-
-        result = []
-        for row_index, row in enumerate(m.elements):
-            for col_index, item in enumerate(row.elements):
-                if row_index == 0:
-                    result.append([item])
-                else:
-                    result[col_index].append(item)
-        return ListExpression(*[ListExpression(*row) for row in result])
+        return eval_Transpose2D(m)
 
 
 class ConjugateTranspose(Builtin):

mathics/core/atoms.py

@@ -739,6 +739,10 @@ def __new__(cls, real, imag):
                 f"Argument 'image' must be an Integer, Real, or Rational type; is {imag}."
             )
 
+        # Note: for the below test, imag.value == 0 catches more
+        # reals.  In particular, MachineReals that have an imaginary
+        # value of floating point 0.0. But MachineReal 0.0 is "approximate 0",
+        # not exactly 0. So "Complex[0., 0.]" is "0. + 0." and not "0."
         if imag.sameQ(Integer0):
             return real
 

mathics/core/builtin.py

@@ -573,20 +573,23 @@ def __init__(self, *args, **kwargs):
             self.sympy_name = strip_context(self.get_name()).lower()
         self.mathics_to_sympy[self.__class__.__name__] = self.sympy_name
 
-    def is_constant(self) -> bool:
-        return False
-
     def get_sympy_names(self) -> List[str]:
         if self.sympy_name:
             return [self.sympy_name]
         return []
 
-    def to_sympy(self, expr=None, **kwargs):
-        raise NotImplementedError
+    def is_constant(self) -> bool:
+        """Returns true if the value of evaluation of this object can
+        never change.
+        """
+        return False
 
     def from_sympy(self, elements: Tuple[BaseElement, ...]) -> Expression:
         raise NotImplementedError
 
+    def to_sympy(self, expr=None, **kwargs):
+        raise NotImplementedError
+
 
 # This has to come before MPMathFunction
 class SympyFunction(SympyObject):