Modifying Class Object
in [Python]
|
From: Steven D'Aprano on 14 Feb 2010 00:13 On Sat, 13 Feb 2010 20:11:06 -0800, Steve Howell wrote: > For a suitably wide definition of pointers CPython does indeed have > pointers, and your example is only a weaker case of that truth. There > is no reductio adsurbum. If I argued that CPython had curly braced > syntax that would be absurd, since it is so concretely wrong. Pointers > are a more abstact concept. I would argue that your examples are equivalent. The suitably wide definition of pointers that allows you to argue that Python has pointers is an implementation detail, just as the implementation detail that the Python tokenizer uses INDENT and DEDENT tokens. An INDENT token is just another way of spelling { and DEDENT is just another way of spelling }, so therefore Python has curly bracket syntax. Do I believe this argument is valid? No, of course not, I think it does so much violence to the concepts of curly brackets and syntax as to be absurd. Just as I think the only way to justify claiming that Python has pointers is to do so much violence to the concept of pointer and to Python's object model as to also be absurd. That's not to say that the general concept of references (as in "to refer to") isn't valuable when discussing Python. If you want to say that (e.g.) following x = 1 the name "x" refers to (or even points to!) the object 1, my objections will be mild or non-existent. In that sense, it's probably impossible to program without some sort of "references": the computer manipulates variables or objects directly, while we manipulate characters in source code. The only way to write a program is to use some abstract thing (a name, an offset, whatever) that refers, in some fashion, to a collection of bits in the computer's memory. But to go from that to the idea that (say) x is a pointer does so much violence to the concept of pointer and has so much room for confusion that it is actively harmful. -- Steven
From: Steve Howell on 14 Feb 2010 00:33 On Feb 13, 9:13 pm, Steven D'Aprano <st...(a)REMOVE-THIS- cybersource.com.au> wrote: > On Sat, 13 Feb 2010 20:11:06 -0800, Steve Howell wrote: > > For a suitably wide definition of pointers CPython does indeed have > > pointers, and your example is only a weaker case of that truth. There > > is no reductio adsurbum. If I argued that CPython had curly braced > > syntax that would be absurd, since it is so concretely wrong. Pointers > > are a more abstact concept. > > I would argue that your examples are equivalent. > > The suitably wide definition of pointers that allows you to argue that > Python has pointers is an implementation detail, just as the > implementation detail that the Python tokenizer uses INDENT and DEDENT > tokens. An INDENT token is just another way of spelling { and DEDENT is > just another way of spelling }, so therefore Python has curly bracket > syntax. > You seem to be missing the point that "curly braces" is a concrete term that very specifically applies to spelling. > Do I believe this argument is valid? No, of course not, I think it does > so much violence to the concepts of curly brackets and syntax as to be > absurd. Just as I think the only way to justify claiming that Python has > pointers is to do so much violence to the concept of pointer and to > Python's object model as to also be absurd. > > That's not to say that the general concept of references (as in "to refer > to") isn't valuable when discussing Python. If you want to say that > (e.g.) following > > x = 1 > > the name "x" refers to (or even points to!) the object 1, my objections > will be mild or non-existent. In that sense, it's probably impossible to > program without some sort of "references": the computer manipulates > variables or objects directly, while we manipulate characters in source > code. The only way to write a program is to use some abstract thing (a > name, an offset, whatever) that refers, in some fashion, to a collection > of bits in the computer's memory. But to go from that to the idea that > (say) x is a pointer does so much violence to the concept of pointer and > has so much room for confusion that it is actively harmful. > I agree that "reference" is a much better term than "pointer.". It has the right amount of generalness in my opinion. I think "violence" is a bit overstated, but your bigger point is well taken and it seems like "reference" is useful middle ground between pure cpython language and misrepresentative analogy.
From: Steven D'Aprano on 14 Feb 2010 02:21 On Sat, 13 Feb 2010 21:33:50 -0800, Steve Howell wrote: > You seem to be missing the point that "curly braces" is a concrete > term that very specifically applies to spelling. And you seem to be missing the point that "pointer" is also a concrete term that very specifically applies to, well, pointers. [...] > I agree that "reference" is a much better term than "pointer.". It has > the right amount of generalness in my opinion. I think "violence" is a > bit overstated, but your bigger point is well taken and it seems like > "reference" is useful middle ground between pure cpython language and > misrepresentative analogy. But reference also has a concrete meaning: C++ has a type explicitly called "reference": http://en.wikipedia.org/wiki/Reference_(C++) And of course call-by-reference (or pass-by-reference) has a specific, technical meaning. -- Steven
From: Alf P. Steinbach on 14 Feb 2010 02:40 * Steven D'Aprano: > On Sat, 13 Feb 2010 21:33:50 -0800, Steve Howell wrote: > >> You seem to be missing the point that "curly braces" is a concrete >> term that very specifically applies to spelling. > > And you seem to be missing the point that "pointer" is also a concrete > term that very specifically applies to, well, pointers. > > [...] >> I agree that "reference" is a much better term than "pointer.". It has >> the right amount of generalness in my opinion. I think "violence" is a >> bit overstated, but your bigger point is well taken and it seems like >> "reference" is useful middle ground between pure cpython language and >> misrepresentative analogy. > > But reference also has a concrete meaning: C++ has a type explicitly > called "reference": > > http://en.wikipedia.org/wiki/Reference_(C++) > > And of course call-by-reference (or pass-by-reference) has a specific, > technical meaning. Hm. Consider your argument about "reference" being possible to confuse with "pass by reference" in the light of "pass by name", used by Algol, <url: http://en.wikipedia.org/wiki/Jensen%27s_Device>. Oops, to consistently remove all possible ambiguity the term "name" can't be used about formal arguments. I think, even though "pass by name" is much less well known than "pass by reference", this indicates that it's not practically possible to remove all possible ambiguity. I think some Common Sense(TM) must in any case be assumed, and applied. Cheers, - Alf
From: Steve Howell on 14 Feb 2010 02:45
On Feb 13, 11:21 pm, Steven D'Aprano <st...(a)REMOVE-THIS- cybersource.com.au> wrote: > On Sat, 13 Feb 2010 21:33:50 -0800, Steve Howell wrote: > > You seem to be missing the point that "curly braces" is a concrete > > term that very specifically applies to spelling. > > And you seem to be missing the point that "pointer" is also a concrete > term that very specifically applies to, well, pointers. > The term "pointer" is very abstract. Please give me a concrete definition of a pointer. A curly brace is one of these: { } Pretty concrete, I hope. > [...] > > > I agree that "reference" is a much better term than "pointer.". It has > > the right amount of generalness in my opinion. I think "violence" is a > > bit overstated, but your bigger point is well taken and it seems like > > "reference" is useful middle ground between pure cpython language and > > misrepresentative analogy. > > But reference also has a concrete meaning: C++ has a type explicitly > called "reference": > > http://en.wikipedia.org/wiki/Reference_(C++) > Of course, "reference" has concrete meanings in specific contexts. But I can refer you to much more general and abstract uses of the term "reference." Do you want references? I will be happy to refer you to appropriate references. > And of course call-by-reference (or pass-by-reference) has a specific, > technical meaning. > Which is what? |