On 5/1/2011 4:45 AM, Steven D'Aprano wrote:
Python uses a data model of "name binding" and "call by object"
(also known as "call by sharing"). I trust I don't need to define my
terms, but just in case:
http://effbot.org/zone/call-by-object.htm
http://effbot.org/zone/python-objects.htm
Now, this is different from languages like C and Pascal, which is
based on variables,
Or Fortran or Basic (and I suspect, but do not know, Algol) and other
descendents: Ada?, PL/1?). In statistical languages, user-defined names
typically refer to typed data columns (eash a set of storage locations)
or user-defined functions.
"Python's data model is different from other languages"
which is perfectly correct, if you think of C as "other languages".
But it's equally correct to say that Python's data model is the same
as other languages.
You defined Python's 'data model' as having two aspects: 'name binding'
and 'call by object'. A language could match one but not the other. I
believe Lisps have name-binding, but I know not all only have
call-object. Macro calls (and earlier predecessors) are call-by-code-text.
As I understand it, Python and Ruby have the same
data model. So does Java, so long as you only consider objects and
ignore unboxed native values. I believe (but could be wrong) that
another language of about the same vintage as Python, Emerald, also
uses the same model. That's not surprising, because I believe that
Emerald (just like Python) was strongly influenced by CLU.
While Guido does not, that I know of, credit CLU as Python's direct
inspiration, I think it (and Barbara Liskov) as the originator of
Python's data model. I believe she thought of the call-by-object
semantics as something of an innovation.
What other languages use the same, or mostly similar, data model as
Python?
Natural languages. That is why I think it is better to think of Python
as an algorithm language or information-object manipulation language
rather than as just a linear-memory machine language. A linear memory
with bytes addressed from 0 to max-int or max-long is an explicit part
of the definition of assembly languages and C. It is no part of the
definition of Python.
Nice begin-a-thread post.
--
Terry Jan Reedy
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