2010-11-14

oop with frameworks

10.23: adda/oop/the 3 layers:
. Padlipsky, author of
The Elements of Networking Style:
"(If you know what you're doing,
three layers is enough...)

. oop'ing needs only 3 layers,
not endless inheritance ?
that reminds how I saw oop as simply
a layer under structured programming: [11.14:
the 1980's structured paradigm meant that
programs could create vocabularies with functions;
but they could create class types
like the native types that were provide
where there was the use of binary ideograms
and implicit coercions among related types .
. the types were provided,
then you built your vocabulary of functions
on top of those types .]
. at that time,
I had not yet thought about frameworks ...

. one place where many levels of
inheritance can be appreciated,
is within the system it was modeled after:
biological classifications of animals
involving inherited features or behaviors .

. I would say the 3rd layer of Padlipsky's oop
is the type cluster, just as type Number is
for the numeric subtypes {R,Q,N,Z,C};
notice the Number type.class is not abstract;
it has the code that handles binary operations, [11.14:
and diff's in operand subtype;
eg, you don't coerce an int to rational
if the rational's value happens to be integral .]
. objects can interact with each other based on
having context menu's which include
recognized submenu's .
. this is programming to interfaces,
and doesn't involve the impl'inheritance
that is usually associcated with oop .

. in summary, the 3 layers of oop are:
#1: a type having an interface to share;
#2: a type claiming to adopt a shared interface;
#3: an app that instantiates interface adopters .

. frameworks are a sort of
structured programming with generics;
you can think of generics as a
layer under stuctured code,
parallel with type.classes .
[11.14:
. a structure library
gives you a language of functions
which you may compose in various ways;
ie, the library is an employee,
and you're the exec .
. a framework library takes the exec' seat
letting you customize its decisions
with your own structure library .
. a datatype is like a structure library
but it's purpose is to control modifications
to the obj's it will create .]