Fix getting string representation of sage objects

Author: isuruf

symengine/lib/pywrapper.cpp

@@ -175,17 +175,12 @@ RCP<const Number> PyNumber::eval(long bits) const {
 }
 
 std::string PyNumber::__str__() const {
-    PyObject* temp;
-    std::string str;
-#if PY_MAJOR_VERSION > 2
-    temp = PyUnicode_AsUTF8String(pyobject_);
-    str = std::string(PyBytes_AsString(temp));
-#else
-    temp = PyObject_Str(pyobject_);
-    str = std::string(PyString_AsString(temp));
-#endif
-    Py_XDECREF(temp);
-    return str;
+    Py_ssize_t size;
+    PyObject *pystr = PyObject_Str(pyobject_);
+    const char* data = PyUnicode_AsUTF8AndSize(pystr, &size);
+    std::string result = std::string(data, size);
+    Py_XDECREF(pystr);
+    return result;
 }
 
 // PyFunctionClass

symengine/lib/symengine_wrapper.pyx

@@ -2690,7 +2690,7 @@ class FunctionSymbol(Function):
     def _sage_(self):
         import sage.all as sage
         name = self.get_name()
-        return sage.function(name, *self.args_as_sage())
+        return sage.function(name)(*self.args_as_sage())
 
     def func(self, *values):
         name = self.get_name()
@@ -2711,7 +2711,7 @@ cdef rcp_const_basic pynumber_to_symengine(PyObject* o1):
 
 cdef PyObject* symengine_to_sage(rcp_const_basic o1):
     import sage.all as sage
-    t = sage.SR(c2py(o1)._sage_())
+    t = c2py(o1)._sage_()
     Py_XINCREF(<PyObject*>t)
     return <PyObject*>(t)
 
@@ -2765,7 +2765,10 @@ cdef class PyNumber(Number):
 
     def _sage_(self):
         import sage.all as sage
-        return sage.SR(self.pyobject())
+        res = self.pyobject()
+        if hasattr(res, '_sage_'):
+            return res._sage_()
+        return res
 
     def pyobject(self):
         return <object>deref(symengine.rcp_static_cast_PyNumber(self.thisptr)).get_py_object()

symengine/tests/test_sage.py

@@ -66,9 +66,9 @@ def test_sage_conversions():
     assert cos(x1)._sage_() == sage.cos(x)
     assert cos(x1) == sympify(sage.cos(x))
 
-    assert function_symbol('f', x1, y1)._sage_() == sage.function('f', x, y)
+    assert function_symbol('f', x1, y1)._sage_() == sage.function('f')(x, y)
     assert (function_symbol('f', 2 * x1, x1 + y1).diff(x1)._sage_() ==
-            sage.function('f', 2 * x, x + y).diff(x))
+            sage.function('f')(2 * x, x + y).diff(x))
 
     assert LambertW(x1) == LambertW(x)
     assert LambertW(x1)._sage_() == sage.lambert_w(x)
@@ -142,11 +142,7 @@ def test_sage_conversions():
     b = b + 8
     assert isinstance(b, PyNumber)
     assert b._sage_() == a
-
-    a = a + x
-    b = b + x
-    assert isinstance(b, Add)
-    assert b._sage_() == a
+    assert str(a) == str(b)
 
     # Sage Function
     e = x1 + wrap_sage_function(sage.log_gamma(x))

symengine/tests/test_sympy_conv.py

@@ -760,6 +760,7 @@ def test_pynumber():
     assert isinstance(b, PyNumber)
     assert b == a                  # Check equality via SymEngine
     assert a == b                  # Check equality via SymPy
+    assert str(a) == str(b)
 
     a = 1 - a
     b = 1 - b