Remove fractional binding

We will be open sourcing NengoSPA under the GPLv2 license.
Fractional binding is patent protected so we are removing it
so that users do not use patented systems without realizing it.

README.rst

@@ -37,7 +37,6 @@ Feature highlights
   structures. Different binding operations/algebras can be mixed in a single
   model.
 - Seamless integration with non-SPA Nengo models.
-- Binding powers and fractional bindings.
 
 
 Project status

docs/modules/nengo_spa.algebras.rst

@@ -23,7 +23,6 @@ Base classes
 
 .. automodule:: nengo_spa.algebras.base
    :members:
-   :show-inheritance:
    :undoc-members:
 
    .. autosummary::
@@ -40,7 +39,6 @@ Holographic reduced representations (HRR)
 
 .. automodule:: nengo_spa.algebras.hrr_algebra
    :members:
-   :show-inheritance:
    :undoc-members:
 
    .. autosummary::
@@ -55,7 +53,6 @@ Vector-derived transformation binding (VTB)
 
 .. automodule:: nengo_spa.algebras.vtb_algebra
    :members:
-   :show-inheritance:
    :undoc-members:
 
    .. autosummary::
@@ -70,7 +67,6 @@ Transposed vector-derived transformation binding (TVTB)
 
 .. automodule:: nengo_spa.algebras.tvtb_algebra
    :members:
-   :show-inheritance:
    :undoc-members:
 
    .. autosummary::

docs/user-guide.rst

@@ -7,4 +7,3 @@ User Guide
    examples/intro-coming-from-legacy-spa.ipynb
    examples/custom-module.ipynb
    user-guide/algebras
-   user-guide/fractional-binding

nengo_spa/ast/symbolic.py

@@ -138,11 +138,6 @@ def __truediv__(self, other):
         type_ = infer_types(self, other)
         return PointerSymbol(self._expr_tree / other._expr_tree, type_)
 
-    @symbolic_op
-    def __pow__(self, other):
-        type_ = infer_types(self, other)
-        return PointerSymbol(self._expr_tree**other._expr_tree, type_)
-
     def dot(self, other):
         other = as_symbolic_node(other)
         if not isinstance(other, PointerSymbol):

nengo_spa/ast/tests/test_symbolic.py

@@ -73,17 +73,6 @@ def test_binary_operation_on_pointer_symbols(op, rng):
     assert_equal(node.output, vocab.parse("A" + op + "B").v)
 
 
-@pytest.mark.parametrize("scalar", [3, np.float64(3)])
-def test_pow_operation_on_pointer_symbols(scalar, rng):
-    vocab = spa.Vocabulary(16, pointer_gen=rng)
-    vocab.populate("A")
-
-    with spa.Network():
-        x = eval("PointerSymbol('A', TVocabulary(vocab)) ** scalar")
-        node = x.construct()
-    assert_equal(node.output, vocab.parse("A ** 3").v)
-
-
 def test_pointer_symbol_mul_with_array():
     with pytest.raises(TypeError):
         PointerSymbol("X") * np.array([1, 2])