Python to C++ translation?

[George Sakkis]

"Mangabasi" <mangabasi at gmail.com> wrote:

> Hi there,
>
> I need to translate the following code (rather something similar) to
> C++.  I have been studying C++ for the last two days but I could not
> find an easy way to do the following Python snippet.
>
>
> class A:
>     def __init__(self, x):
>         self.x = x
>     def methodA():
>         pass # Ignore the details
> class B:
>     def __init__(self, x):
>         self.x = x
>     def methodB():
>         def methodB():
>             pass # Ignore the details
> class C:
>     def __init__(self, A, B):
>         self.A = A
>         self.B = B
>
> a = A(5)
> b = B(5.5)
> c = C(a, b)
> print c.A.x
> print c.B.x
> #so far I can do it in C++
> #how do I do the following in C++?
> d = C(b, a)
> print d.A.x
> print d.B.x

In python this works thanks to "duck typing"; as long as both A and B instances have an attribute
'x', A.x and B.x work as expected without the need for type declarations. In C++ (and other
statically typed languages) there is no duck typing, so you can't translate it from python verbatim.
The typical (if not only) way to achieve the same in C++ is to have A and B inherit from a common
parent class, say X, and drag the common interface and implementation of A and B to X. Of course you
could (or perhaps should) do the same in python:

class X:
     def __init__(self, x):
         self.x = x

class A(X):
     def methodA():
         pass # Ignore the details

class B(X):
     def methodB():
        pass # Ignore the details

class C:
     def __init__(self, x1, x2):
         self.x1 = x1
         self.x2 = x2

So the constructor of C would take two X instances, and the respective attributes x1 and x2 would be
declared as pointers to X.

HTH

George