Add attribute to Dummy: dummy_index

Author: bjodah

symengine/lib/symengine.pxd

@@ -133,6 +133,7 @@ cdef extern from "<symengine/basic.h>" namespace "SymEngine":
     RCP[const Rational] rcp_static_cast_Rational "SymEngine::rcp_static_cast<const SymEngine::Rational>"(rcp_const_basic &b) nogil
     RCP[const Complex] rcp_static_cast_Complex "SymEngine::rcp_static_cast<const SymEngine::Complex>"(rcp_const_basic &b) nogil
     RCP[const Number] rcp_static_cast_Number "SymEngine::rcp_static_cast<const SymEngine::Number>"(rcp_const_basic &b) nogil
+    RCP[const Dummy] rcp_static_cast_Dummy "SymEngine::rcp_static_cast<const SymEngine::Dummy>"(rcp_const_basic &b) nogil
     RCP[const Add] rcp_static_cast_Add "SymEngine::rcp_static_cast<const SymEngine::Add>"(rcp_const_basic &b) nogil
     RCP[const Mul] rcp_static_cast_Mul "SymEngine::rcp_static_cast<const SymEngine::Mul>"(rcp_const_basic &b) nogil
     RCP[const Pow] rcp_static_cast_Pow "SymEngine::rcp_static_cast<const SymEngine::Pow>"(rcp_const_basic &b) nogil
@@ -180,7 +181,7 @@ cdef extern from "<symengine/symbol.h>" namespace "SymEngine":
         Symbol(string name) nogil
         string get_name() nogil
     cdef cppclass Dummy(Symbol):
-        pass
+        size_t get_index()
 
 cdef extern from "<symengine/number.h>" namespace "SymEngine":
     cdef cppclass Number(Basic):

symengine/lib/symengine_wrapper.in.pyx

@@ -1355,6 +1355,12 @@ cdef class Dummy(Symbol):
     def func(self):
         return self.__class__
 
+    @property
+    def dummy_index(self):
+        cdef RCP[const symengine.Dummy] this = \
+            symengine.rcp_static_cast_Dummy(self.thisptr)
+        cdef size_t index = deref(this).get_index()
+        return index
 
 def symarray(prefix, shape, **kwargs):
     """ Creates an nd-array of symbols

symengine/tests/test_symbol.py

@@ -156,6 +156,7 @@ def test_dummy():
     x2 = Symbol('x')
     xdummy1 = Dummy('x')
     xdummy2 = Dummy('x')
+    assert xdummy1.dummy_index != xdummy2.dummy_index  # maybe test using "less than"?
 
     assert x1 == x2
     assert x1 != xdummy1