[Tutor] Pair 'o dimes wuz: Volunteer teacher

[Alan Gauld]

On 24/07/2022 12:23, Leam Hall wrote:

> First, Python is a lot easier to read than many languages. 

True but that only really helps when working at the detail level. It
does nothing to help with figuring out how a system works - which
functions call which other functions. How  data structures relate to
each other etc. And thats where design comes in. One of the big failures
in design is to go too deep and try to design every line of code. Design
should only go to the level where it becomes easier to write code than
design. When that stage is reached it is time to write code!

> Imagine the dev team trying to work through a spaghetti of 
> undesigned codebase, and the design person saying "Now do 
> you believe me that design is important?" 

I've been there several times. We once received about 1 million
lines of C code with no design. We had a team of guys stepping
through the code in debuggers for 6 months documenting how it
works and reverse engineering the "design". it took us 3 years
to fully document the system. But once ew did we could turn around
bugs in 24 hours and new starts could be productive within 2 days,
rather than the 2 or 3 months it took when we first got the code!

When I ran a maintenance team and we took on a new project one of
the first tasks was to review the design and if necessary update
it (or even rewrite it) in a useful style. A good design is
critical to efficient maintenance, even if it has to be retro-fitted.

> Unfortunately, we can't just open our skulls up, drop in the GoF 
> or Booch's OOAD, and magically do good design.

Absolutely true. You need to start with the basics.
Branching, loops, functions, modules, coupling v cohesion.
Separation of concerns, data hiding. Clean interface design.
Then you build up to higher level concepts like state machines,
table driven code, data driven code, data structures and
normalisation.

And even if using a book like Booch (which is very good) it
should be woked through in parallel with the language constructs.
But just as reading booch alone would be useless, so is learning
to define functions without understanding their purpose. Or
building classes without understanding why.

Learning is an iterative process. And this is especially
true with software. But you need to understand the why
and how equally. Learning how without knowing why leads to bad
programming practices - global variables, mixing logic and
display, tight coupling  etc.

> Once we have the basics, hopefully a mentor shows up 

Ideally we have the mentor in place before we even look at the basics.
Even the basics can be baffling without guidance.
I've see so many beginners completely baffled by a line like:

x = x + 1

It makes no sense to a non-programmer. It is mathematical nonsense!
(Its also my many languages have a distince assignment operator:

x := x+1

is much easier to assimilate....

> We agree that good design is good. My opinion, even if it's mine alone, 
> is that design is not the first thing to learn.

I dont think I'm arguing for design as a skill - certainly not
things like UML or SSADM or even flow charts. But rather the
rationale behind programming constructs. Why do we have loops?
Why so many of them? And why are functions useful? Why not just
cut 'n paste the code?

For OOP it's about explaining why we want to use classes/objects.
What does an OOP program look like - "a set of objects communicating
by messages". How do we send a message from one object to another?
What happens when an object receives a message? What method does
the receiver choose to fulfil the message request? How does
the receiver reply to the requestor? These ideas can then be
translated/demonstrated in the preferred language.

A decent OOAD book will describe those concepts better than a
programming language tutorial in my experience. (Again, the
first section of Booch with its famous cat cartoons is very
good at that)

-- 
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:
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