Typo fixes in doc

doc/extending/ctype.txt

@@ -558,9 +558,9 @@ default, it will recompile the c code for each process.
 Shape and Shape_i
 =================
 
-We have 2 generic Ops Shape and Shape_i that return the shape of any
-Theano Variable that have a shape attribute and Shape_i return only of
-the element of the shape.
+We have 2 generic Ops, Shape and Shape_i, that return the shape of any
+Theano Variable that has a shape attribute (Shape_i returns only one of
+the elements of the shape).
 
 
 .. code-block:: python
@@ -568,5 +568,5 @@ the element of the shape.
    theano.compile.ops.register_shape_c_code(YOUR_TYPE_CLASS, THE_C_CODE, version=())
    theano.compile.ops.register_shape_i_c_code(YOUR_TYPE_CLASS, THE_C_CODE, version=())
 
-The c code work as the ViewOp. Shape_i have the additional i parameter
-that you can use with %(i)s.
+The C code works as the ViewOp. Shape_i has the additional ``i`` parameter
+that you can use with ``%(i)s``.