[J3] What is an entity?
Kurt W Hirchert
kurthirchert at gmail.com
Sat Aug 13 19:03:36 UTC 2022
On 8/13/2022 2:55 AM, Thomas König via J3 wrote:
> "Entity" is used in several definitions in "Terms and Definitions"
> and also in other places, but I didn't find in the standard.
>
> I would assume that "entities" refers to variables, constants and
> anything else that can hold data, but maybe it is something that
> could be more clearly defined.
That assumption is incomplete. The word "entity" was introduced into
the draft of Fortran 90 as a more respectable replacement for what we
had been calling "thingo" in committee discussions. (For those informal
discussions, the committee could just as easily have used
"whatchamacallit", or "thingamabob", or , if correctly understood what I
heard on "Says You" the morning, "oojah".) The point was to allow
discussion of supporting patterns of behavior or usage without limiting
that discussion to things encompassed by a particular technical term.
It was intentionally not given a technical definition, but left as an
English language placeholder.
The classic example of this usage of "entity" is in the description of
modules. The intent was that modules should be a universal mechanism
for sharing anything that needs to be shared among multiple program
units. Currently, that includes variables, name constants, defined
types, specific names for procedures, and generic identifiers for groups
of related procedures, but if the committee were to add a new class of
things worth sharing, such as named exceptions or named macros, all that
would be needed to allow this sharing would be to provide whatever
syntactic hooks are needed to put them in a module. After that, the
descriptions of module and the effects of the USE statement
automatically extend to those things because a module is used to share
_entities_. (If you prefer a historical example, when the committee
added procedure pointers to the language, it was more or less automatic
that they were sharable via modules without requiring an separate action
by the committee in that regard.)
I suppose one could add an entry for "entity" in the Terms and
Definitions to point out that it is not a defined technical term, but is
used in its usual English language sense, but I don't know whether that
would be an improvement.
-Kurt
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