etymology of "list comprehension"?

"Martin v. Löwis" martin at v.loewis.de
Fri Nov 7 07:26:43 CET 2008


mh at pixar.com wrote:
> Chris Rebert <clp at rebertia.com> wrote:
>> the term
>> "comprehension" for the concept was first used in the NPL programming
>> language (Wikipedia again).
> 
> Ah, thanks... and does "comprehension" have any special computer
> science meaning?

Paul already explained the maths, but I find that the etymology remains
unclear still. In any case, the Wikipedia article
Axiom_schema_of_specification says that the following names are used
for this axiom:
- axiom schema of specification,
- axiom schema of separation,
- subset axiom scheme or
- axiom schema of restricted comprehension

I think the "comprehension" definition goes back to this definition from
logic:

# In logic, the comprehension of an object is the totality of
# intensions, that is, attributes, characters, marks, properties, or
# qualities, that the object possesses, or else the totality of
# intensions that are pertinent to the context of a given discussion.

So you get an "intensional" definition of a set: give me all object
with a certain comprehension - as opposed to "extensional" definition,
such as "the set of all capitals consists of Paris, London, Berlin,
Madrid, ..."

The definition in logic, in turn, matches my understanding of the
English word "to comprehend": If I know all attributes, marks,
etc of an object, I understand it fully, i.e. I comprehend it.

Regards,
Martin



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