[Tutor] Inheritance in Python

[Manprit Singh]

Dear sir,

So if I say that combinational digital logic circuits can be  realised
efficiently in the form.of functions..since output depends on input only.

There is another group called sequential circuits....examples are latches,
flip- flops etc  , classes can be used in such cases ? There is feedback
involved in such circuits .

If yes.. then let me try to write a code for sr latch .

Hope of I am right you don't mind finding issues in my code written for sr
latch as a class.

Regards
Manprit singh



On Thu, 10 Sep, 2020, 19:17 Alan Gauld via Tutor, <tutor at python.org> wrote:

> On 10/09/2020 13:46, Manprit Singh wrote:
>
> > half adder is a combinational logic circuit , which can generate Sum and
> > Carry output for 2 input  bits . Table given below describes the output
> of
> > half adder
> >
> > Inp1    Inp2       SUM        Carry
> > 0         0             0              0
> > 0         1             1              0
> > 1         0             1              0
> > 1         1             0              1
> >
> > It is clear from the table that  SUM  bit is generated with bitwise
> > Exclusive OR and Carry bit is generated with bitwise AND .
> >
> > So coming to the question,  IF  there are two classes one for bitwise AND
> > and second for bitwise Exclusive OR operation. and i have to make a class
> > for half adder , if i am not wrong i can use inheritance for deriving a
> > new  class for half adder from existing classes  of bitwise AND and
> Bitwise
> > OR operation.
> >
> > Need your guidance .
> >
>
> Everything is possible but not everything is a good idea.
> Inheritance is intended to reflect the concept of an "is-a"
> relationship. So subclasses should have the same interface
> as the superclass (possibly with some extensions).
>
> So the question is: Does a half adder look like an xor or
> and gate to the user? Is the interface similar. Could you
> use them interchangeably? Insofar as they both have two
> inputs yes, but the gates only have one output whereas
> the half-adder has 2.
>
> There is another form of structure in OOP, namely composition.
> Is it not more accurate to say that the half-adder *contains*
> an and gate and an xor gate?
>
> I appreciate that you are using concepts with which you are
> familiar to learn about OOP. However the problem with these
> logic gate examples is that they are really just functions.
> You can write a function that returns the logical result of
> two (or more) inputs and it would be just as effective as
> a class - and no need to create instances.
>
> def AND(*in): return all(in)
>
> def XOR(x,y): return x^y   # multiple inputs is trickier.
>
> def half_adder(x,y): return (XOR(x,y),AND(x,y)
>
> sum,carry = half_adder(1,1)
>
>
> Classes are best used for things that have state - consider
> a bistable, or latching or FIFO buffer, or similar component.
> There the output depends on the previous inputs.
>
> Gates can be represented as objects if you were building say
> a CAD system with multiple components joined together. Then
> you might want to store references to the connected components
> and pass the output signals into these. But that is quite a
> complex simulation to write since you need to add clocks etc.
>
> --
> Alan G
> Author of the Learn to Program web site
> http://www.alan-g.me.uk/
> http://www.amazon.com/author/alan_gauld
> Follow my photo-blog on Flickr at:
> http://www.flickr.com/photos/alangauldphotos
>
>
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