2014-11-30

the value of constants

2.20: news.adda/co/the value of constants:
11.30: summary:
. in classical programming constants are encouraged
because it simplifies the programming space:
you are no longer concerned with
accidently modifying a constant object
because the compiler or the hardware
will automatically detect that mistake for you .
. constants have even more usefulness
in the context of cloud computing .

Google Cloud Storage Python API Overview:
"Cloud Storage is useful for
storing and serving large files
because it does not have a size limit
for your objects.
... Once you have created an object,
it cannot be modified.
To modify an existing object,
you need to overwrite the object
with a new object that contains your desired changes."
-- [. this behavior is typical of oop systems;
there are variable objects which are pointers to
a sequence of constant value objects;
and the fact that they are constants
allows them to be shared by multiple pointers .
. what makes it useful in the cloud
is that more distributed computing is possible:
it is easier to separate pieces of the code
and run them concurrently, because
they are communicating less via variables .]

scalability and security:
With App Engine apps, the ‘local’ filesystem
— the project directory tree,
which is uploaded with your deployed app —
is read-only.
This constraint is imposed for
scalability and security reasons;
sometimes it’s referred to as ‘sandboxing’.
[ but this page gives as an example of rom,
that you can perform normal writes on files,
but you can't do appends of files,
because that would be a modifying operation,
whereas if you have a file write,
that file name has been assigned a new object
(a different file id).]