Darren New <dne### [at] sanrrcom> wrote:
> Consider the case of "class alpha 
> {int abc;}" for a counter-example - I know exactly how that's laid out due 
> to the standard.

  I don't think the standard specifies what kind of padding the compiler
will use between member elements.

  For example, if you have a "struct { char c; int i; };", how many bytes,
if at all, are there between 'c' and 'i'?
  Suppose you have "struct { int i; long l; };" in a 64-bit system. Will
the compiler put padding bytes between 'i' and 'l' or not?

  Suppose you have:

class A {};
class B: public A { int i; };

  sizeof(A) will be, per the C++ standard, at least 1. But what will be
sizeof(B), and consequently the offset of 'i' inside it? The standard
doesn't specify, and the compiler is free to optimize the empty base
class away or not, as it sees fit.

  Oh, and it becomes even more complicated:

class A { int i1; public: virtual ~A(); };
class B1: virtual public A { int i2; };
class B2: virtual public A { int i3; };
class C: public B1, public B2 { int i4; };

  Want to start guessing the offsets of the ints inside C? Good luck.

-- 
                                                          - Warp

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Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
> >   You always succeed in returning to your favorite subject: Bashing
> > "unsafe" languages. And in your world there's only one such language: C++.

> You know something?  It's getting "really tiresome and old" that every time 
> I list problems with 5 or 6 different languages, you think I'm bashing on 
> C++.

  5 or 6 different languages? Really?

  You started by making a reference to "unsafe languages" within the subject
of modular programming as a reply to one of my posts (clearly as a reference
to C++), and later you said that C++ is the *only* unsafe OO language you
know of. After that you have been done nothing else than arguing why
modularity in C++ is broken and why Lisp, Java and C# are so great.

  It was certainly not me who brought up C++ into the conversation.

  Yeah, sure. You really have been pointing out problems in "5 or 6 different
languages", and I'm just being paranoid that you are concentrating a little
too much on C++.

> It's getting "really tiresome and old" that every time I point out 
> something that Windows does well, I'm told I'm bashing on Linux.

  Every time? When was the last time?

> It's 
> getting "really tiresome and old" that every time I point out problems with 
> unsafe languages in general, you think I'm bashing solely on C++.

  You explicitly wrote that C++ is the only unsafe OO language you know of.
You have been writing specifically about C++, not about "unsafe languages
in general".

> It's 
> getting "really tiresome and old" that every time I talk about automatic 
> resource management you think I'm bashing C++. It's getting "really tiresome 
> and old" that most times you tell me I'm ignorant and I ask you for more 
> information, you ignore that request, preferring just to insult me rather 
> than actually provide information that might improve the conversation.

  And it's getting really tiresome and old that you act all innocent after
a tirade of C++ bashing, saying that "I just wanted a serious discussion
and honestly wanted to know more", when it's rather clear that you didn't
really.

  It's also getting tiresome that every time I criticize some other language
you immediately assume I'm defending C++. For example, if I call some other
language "kludgey", you immediately assumed that I'm claiming that C++ is
not, even though I never said anything of the sorts. And of course you
immediately jumped to the opportunity of starting bashing.

-- 
                                                          - Warp

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Nicolas Alvarez <nic### [at] gmailcom> wrote:
> Warp wrote:
> >   It breaks modularity badly. The whole idea of data hiding is that the
> > private part should be completely opaque to the outside. The second it
> > isn't, outside code will start making assumptions, and you can't change
> > the implementation of the class anymore.

> You CAN change the implementation of the class. It's not your problem if you
> break code that made assumptions.

  I don't think that's a good programming principle.

-- 
                                                          - Warp

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Darren New <dne### [at] sanrrcom> wrote:
> There are few other unsafe OOP languages I know enough about to discuss. Ada 
> and C++ are the only unsafe OOP languages I know

  Ok, here's a couple more:

- Objective-C. Regardless of the name, has nothing to do with C++.
- C#. Regardless of the name, has nothing to do with C++.

> >   The connection between my usage of the word "kludge" and your usage
> > of the words "unsafe" and "reflection" is purely your invention.

> OK. I was confused by the fact that your post had
> 1) A paragraph about how CLOS allows access to the private variables,
> 2) a comment about languages lacking data hiding aren't really OO,
> 3) a lack of specific support for hiding means the OO is kludgey.

  I still see no connection to "unsafe" languages and "reflection". Those
were your inventions.

-- 
                                                          - Warp

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
> > Darren New <dne### [at] sanrrcom> wrote:
> >>>> I'm saying that C++ does not enforce that you don't change private instance 
> >>>> variables from outside the class.
> >>>   And this has exactly what to do with whether (compiler-enforced) data
> >>> hiding is a good thing or not?
> > 
> >> Because there's two reasons for data hiding: (1) allow more flexibility in 
> >> implementation, (2) allow easier debugging.
> > 
> >> If you can violate my encapsulation, I don't see the data as especially 
> >> encapsulated, is all.
> > 
> >   You didn't answer my question.

> You said the designs of C# and Java are badly broken because they let you 
> get to the private variables of an instance using reflection. You then said 
> C++ doesn't let you get to a private variable of an instance. I was 
> disputing that claim. That's what compiler-enforced data hiding has to do 
> with C++.

> >   "Is enforced data hiding a good thing or a bad thing?"
> >   "In C++ you can bypass the encapsulation, so it's a bad thing."

> You skipped a bunch of context in between that I thought still applied. 
> Maybe you're reading messages in a different order than I am. That's one of 
> the problems when a conversation really gets going online. :-)

> If you're not going to apply that context, see my other messages where I 
> explain the types of access and seem to be mostly in agreement with you.

> >>>   Every single discussion about programming with you turns into C++ bashing,
> >>> no matter what the subject.

> >> I'm happy to bash any other unsafe OO language you might want to name. :-)

> >   It's getting really tiresome and old.

> I didn't start out bashing C++ this time. We got pretty far until you 
> *seemed to* claim C++ was better at modularity than C# or Java or CLOS. I 
> merely listed C++ amongst a half-dozen languages I was criticizing for 
> different individual design choices.

  You are seriously claiming that when you wrote "like, in unsafe languages,
where a stray pointer can change private variables without going thru the
class methods? :-)" as a reply to my post you were not directly and
exclusively referencing C++, especially with that smiley?

  What other half-dozen "unsafe languages, where a stray pointer can change
private variables" were you talking about there?

-- 
                                                          - Warp

Post a reply to this message

Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> Consider the case of "class alpha 
>> {int abc;}" for a counter-example - I know exactly how that's laid out due 
>> to the standard.
> 
>   I don't think the standard specifies what kind of padding the compiler
> will use between member elements.

It specifies that the first element has no padding before it.

>   For example, if you have a "struct { char c; int i; };", how many bytes,
> if at all, are there between 'c' and 'i'?

That's a different example, yes.  It's going to be compiler/architecture 
dependent.

>   Oh, and it becomes even more complicated:
> 
> class A { int i1; public: virtual ~A(); };
> class B1: virtual public A { int i2; };
> class B2: virtual public A { int i3; };
> class C: public B1, public B2 { int i4; };
> 
>   Want to start guessing the offsets of the ints inside C? Good luck.

I don't think the standard says what the offsets are for classes with 
virtual destructors.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> Warp wrote:
>>>   You always succeed in returning to your favorite subject: Bashing
>>> "unsafe" languages. And in your world there's only one such language: C++.
> 
>> You know something?  It's getting "really tiresome and old" that every time 
>> I list problems with 5 or 6 different languages, you think I'm bashing on 
>> C++.
> 
>   5 or 6 different languages? Really?

Yeah. LISP, Java, C#, C++, Python, and Ada. That's the first post I said 
anything that could conceivably imply C++ wasn't perfect. I pointed out how 
you could violate encapsulation in each of them.

>   You started by making a reference to "unsafe languages" within the subject
> of modular programming as a reply to one of my posts

Yes.

>(clearly as a reference to C++), 

Except I specificly used the phrase "unsafe languages" because I knew if I 
said "C++" you'd go off the handle.  I was particularly pointing out that 
unsafe languages let you violate modularity. Whether it's OO modularity or 
non-OO modularity is irrelevant to whether unsafe languages let you violate 
modularity.

 > and later you said that C++ is the *only* unsafe OO language you
> know of.

But it's not the only unsafe modular language I know. But you were talking 
about OO in addition to modularity, so that's why it came up.

> After that you have been done nothing else than arguing why
> modularity in C++ is broken and why Lisp, Java and C# are so great.

I haven't said the others were great. I simply said I preferred the 
imperfections in C# to the imperfections in C++.

>   Yeah, sure. You really have been pointing out problems in "5 or 6 different
> languages", and I'm just being paranoid that you are concentrating a little
> too much on C++.

Honestly, it really seems like that to me. I'm sorry you have so much of 
your ego bound up in a programming language.

>> It's 
>> getting "really tiresome and old" that every time I point out problems with 
>> unsafe languages in general, you think I'm bashing solely on C++.
> 
>   You explicitly wrote that C++ is the only unsafe OO language you know of.

Yes, after you asked me about it.  I also asked you to name another unsafe 
OO language, but you didn't. There are other OO languages that you can 
bypass the safety on, but most people using them don't without knowing what 
they're doing, specifically for performance.

> You have been writing specifically about C++, not about "unsafe languages
> in general".

No. I was writing about unsafe modular languages. It turned into C++ after a 
while, when people started specifically saying you can't bypass the 
modularity in C++ like you can in the other languages.

>   And it's getting really tiresome and old that you act all innocent after
> a tirade of C++ bashing, saying that "I just wanted a serious discussion
> and honestly wanted to know more", when it's rather clear that you didn't
> really.

Well, if you start out with that assumption, I guess anything I say can be 
twisted to read that way.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> There are few other unsafe OOP languages I know enough about to discuss. Ada 
>> and C++ are the only unsafe OOP languages I know
> 
>   Ok, here's a couple more:
> 
> - Objective-C. Regardless of the name, has nothing to do with C++.

Hmm. Yes, ok, I'd forgotten about that one, since I looked at it way back in 
the NeXT days but never used it. Very good, thanks. That's another example 
of an unsafe OO language where the lack of safety can lead to lack of 
modularity with all the same problems as C++.

> - C#. Regardless of the name, has nothing to do with C++.

C# is only unsafe if you specifically tell it "hey, I'm doing something 
unsafe."  That doesn't really count, any more than a safe language that can 
call out to C libraries is "unsafe".

>   I still see no connection to "unsafe" languages and "reflection". Those
> were your inventions.

Yes. It's part of an ongoing conversation, you see. "Access to private 
members violates encapsulation."   "Yes, and here's other ways to violate 
encapsulation."  See?

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Warp wrote:
>   You are seriously claiming that when you wrote "like, in unsafe languages,
> where a stray pointer can change private variables without going thru the
> class methods? :-)" as a reply to my post you were not directly and
> exclusively referencing C++, especially with that smiley?

Yes. I am seriously claiming that. The smiley is there to say "Gee, I bet 
Warp will assume I'm for some reason attacking him. Maybe I'll try to be 
friendly and head that off."

If I was intentionally tweaking you, I'd use a winky face. :-)

>   What other half-dozen "unsafe languages, where a stray pointer can change
> private variables" were you talking about there?

C, for one. Any of the usually-safe languages that specifically bypass the 
safety features, like Ada using unchecked features or Eiffel with the 
precondition checking compiled out.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> > - C#. Regardless of the name, has nothing to do with C++.

> C# is only unsafe if you specifically tell it "hey, I'm doing something 
> unsafe."  That doesn't really count

  Of course it doesn't.

-- 
                                                          - Warp

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> >   What other half-dozen "unsafe languages, where a stray pointer can change
> > private variables" were you talking about there?

> C, for one.

  Except that C doesn't have private variables.

-- 
                                                          - Warp

Post a reply to this message

Warp escreveu:
> Nicolas Alvarez <nic### [at] gmailcom> wrote:
>> Warp wrote:
>>>   It breaks modularity badly. The whole idea of data hiding is that the
>>> private part should be completely opaque to the outside. The second it
>>> isn't, outside code will start making assumptions, and you can't change
>>> the implementation of the class anymore.
> 
>> You CAN change the implementation of the class. It's not your problem if you
>> break code that made assumptions.
> 
>   I don't think that's a good programming principle.

Me neither.  But that's a bad programming principle by the dumbass 
accessing stuff it shouldn't.  It's not your fault as the module 
provider and is beyond your control.

Post a reply to this message

Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>>> - C#. Regardless of the name, has nothing to do with C++.
> 
>> C# is only unsafe if you specifically tell it "hey, I'm doing something 
>> unsafe."  That doesn't really count
> 
>   Of course it doesn't.

Or, at least, it falls into the same category as using reflection. :-)

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>>>   What other half-dozen "unsafe languages, where a stray pointer can change
>>> private variables" were you talking about there?
> 
>> C, for one.
> 
>   Except that C doesn't have private variables.

Sure it does. Everything in a FILE structure is a private variable. 
Everything on the stack is private variables. You're reading things too 
narrowly.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Warp wrote:
>   You are seriously claiming that when you wrote "like, in unsafe languages,
> where a stray pointer can change private variables without going thru the
> class methods? :-)" as a reply to my post you were not directly and
> exclusively referencing C++, especially with that smiley?

BTW, I think it's at least as realistic a claim as

 >  The connection between my usage of the word "kludge" and your usage
 > of the words "unsafe" and "reflection" is purely your invention.

Seriously, I'm willing to admit we seem to miscommunicate a lot. But telling 
me I'm always misinterpreting you, then telling me I'm lying when I tell you 
you're misinterpreting me is a bit unpleasant.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> He's saying that putting "private:" before the variables in a class 
> declaration is equivalent to naming private variables with an underscore. In 
> the first case, the compiler warns you if you use a private variable by 
> mistake. In the second case, it's obvious from inspection. If you have
>     x._y
> in your code, you're doing something wrong. :-)

  Btw (not flaming here), what would be the naming convention for nested
classes? Take, for example, this kind of situation, in C++ code:

class OuterClass
{
 public:
    // Public interface here.

 private:
    // Outside code should not access anything from this point forwards.
    // This includes the 'InnerClass' class below.

    class InnerClass
    {
     public:
        // Public interface for OuterClass to use.

     private:
        // Private members of InnerClass. OuterClass should not access.
    };
};

  While it becomes complex, it's possible to have even a *third* nested
class, inside 'InnerClass', with the equivalent access rules.

  (Defining 'InnerClass' outside of 'OuterClass' is not a viable solution
if I really want 'InnerClass' to be strictly inside the scope of
'OuterClass' and nowhere else, because my class design calls for this.)

-- 
                                                          - Warp

Post a reply to this message

Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> He's saying that putting "private:" before the variables in a class 
>> declaration is equivalent to naming private variables with an underscore. In 
>> the first case, the compiler warns you if you use a private variable by 
>> mistake. In the second case, it's obvious from inspection. If you have
>>     x._y
>> in your code, you're doing something wrong. :-)
> 
>   Btw (not flaming here), what would be the naming convention for nested
> classes? Take, for example, this kind of situation, in C++ code:

Python is kind of funky in this respect. Nested classes (or functions, or 
etc) don't have access to the private variables of the classes they're 
nested in.  They can only get locals, globals, or built-ins. A lambda 
expression can, but that's not a separate class as such, but just an unnamed 
function.

Depending on which naming convention you're talking about, class beta nested 
inside class alpha would be alpha.beta (if it's a public class), or 
alpha._beta if it's a private class.

In python, classes are values just like strings and lists and such. You can 
even instantiate classes without using the normal syntax, just by invoking 
the appropriate constructor for type "class". The syntax
    class abc:
       ...
just invokes that constructor and assigns the result to the variable abc 
(which creates the variable in that namespace if it doesn't already exist).

So if you nest alpha within beta like this
class beta:
    static_one = 1
    static_two = 2
    def beta_add(self,x,y):
       return x + y
    class alpha:
      root = 27
      def alpha_add(self,x,y):
         return x + y + root
then you get beta.static_one and beta.static_two and beta.beta_add and 
beta.alpha. You also get beta.alpha.root and beta.alpha.alpha_add.
Alpha can't access beta.static_one without using a dot. Beta can access 
alpha (as in "new alpha" sort of thing) without a dot, because alpha is a 
static variable of class beta.

But the namespaces that routines in alpha can access don't include the 
namespace that beta uses, and vice versa.

Hence, to get to alpha from outside of beta there, you need to say beta.alpha.

If you want alpha to be private to beta, so beta is (say) your linked-list 
class and alpha is a single link, you use "class _alpha:" instead, which 
indicates that beta._alpha is meant to be private to beta.

If you want alpha to be public, you name it "class alpha:" and others refer 
to it as beta.alpha.

Does that answer it? I probably gave way more details than you were actually 
asking about. :-)

The same naming convention holds for what you'd call "member variables" in 
C++, member functions, static variables/functions, nested classes, etc. 
Everything gets assigned to a variable. If you want gamma to implement the 
same foobar function as delta does, you can just write
    gamma.foobar = delta.foobar
and they're both the same function afterwards.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> Does that answer it? I probably gave way more details than you were actually 
> asking about. :-)

  I actually didn't understand your answer. There might have been some
miscommunication.

  Let me restate:

  There's a class named 'OuterClass', which has a public interface for
everything else to use, and a private part which is used only by 'OuterClass'
itself, and should be accessed by anything else.

  This private part declares another class named 'InnerClass'. This class
in question is part of the private implementation of 'OuterClass', and thus
should not be used in any way from the outside. However, 'OuterClass' itself
can, naturally, use it as usual.

  However, 'InnerClass' itself also has a public and a private part: The
public part defines the interface for 'OuterClass' to use. The private
part is for the internal implementation of 'InnerClass' itself, and shouldn't
be accessed by 'OuterClass'.

  The question is: If we are using a naming convention to denote public
and private data, how do you name 'InnerClass' and its private members?

  Since 'InnerClass' is part of the private implementation of 'OuterClass'
and thus should be used from the outside, I assume that the convention is
to call it '_InnerClass' (or whatever). The underscore denotes "don't
use this class from outside 'OuterClass', because it's private".

  How how do you name the members of this '_InnerClass'? All of its
members, even those in the public interface, are part of the private
implementation of 'OuterClass' and thus shouldn't be used from outside,
so do you put underscores in all the members, even public ones?

  What about the private members of '_InnerClass'? How do you differentiate
them from the private members of 'OuterClass'?

-- 
                                                          - Warp

Post a reply to this message

Warp wrote:
>   The question is: If we are using a naming convention to denote public
> and private data, how do you name 'InnerClass' and its private members?

Got it.

OuterClass
OuterClass._private_static_of_OC
OuterClass.public_static_of_OC
OuterClass._InnerClass
OuterClass._InnerClass.used_by_outerclass
OuterClass._InnerClass._Used_only_by_innerclass

Does that clarify?

OuterClass could invoke
    x = _InnerClass.used_by_outerclass

The trick is you shouldn't write "._" as part of a reference. :-)

>   How how do you name the members of this '_InnerClass'? All of its
> members, even those in the public interface, are part of the private
> implementation of 'OuterClass' and thus shouldn't be used from outside,
> so do you put underscores in all the members, even public ones?

Oh, no. InnerClass isn't really "part" of outer class. It's just a class 
that happens to be created while creating InnerClass and assigned to a 
static variable of InnerClass.

Python doesn't have declarations, even of classes and functions and methods. 
It has statements that have lumps of code in them and creates an instance of 
a function object or an instance of a class object, and then assigns it to 
the name you gave the statement.  So there's no real relationship between 
InnerClass and OuterClass, any more than you have a relationship between a 
sphere object and the texture on the sphere. There's a relationship there, 
but it's not a relationship having to do with types, but rather with 
pointers to instance objects.  Kind of like javascript in that respect.

>   What about the private members of '_InnerClass'? How do you differentiate
> them from the private members of 'OuterClass'?

The private members of _InnerClass have _ on the front. _InnerClass can't 
access OuterClass's private or public variables without going through the 
class or instance dot-notation.

InnerClass and OuterClass are two 100% separate and independent classes. You 
could get *exactly* the same result by declaring it this way:

class InnerClass:
    .....

class OuterClass:
    ...
    _InnerClass = InnerClass
    ...
(Except of course now InnerClass has a global name also)

A nested class definition says "Create a new instance of type 'class' and 
assign it to this name in my namespace."  But that doesn't give the nested 
class any access that any other class could have, and vice versa. It's just 
a different name for a class. InnerClass doesn't have anything that points 
to the parent class, so there's no way to get to anything in the parent 
class directly from InnerClass. If the parent class has a global name like 
"OuterClass", then you can refer to that, of course, but there's nothing 
that tells InnerClass it's "part of" outerclass.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
> >   The question is: If we are using a naming convention to denote public
> > and private data, how do you name 'InnerClass' and its private members?

> Got it.

> OuterClass
> OuterClass._private_static_of_OC
> OuterClass.public_static_of_OC
> OuterClass._InnerClass
> OuterClass._InnerClass.used_by_outerclass
> OuterClass._InnerClass._Used_only_by_innerclass

> Does that clarify?

> OuterClass could invoke
>     x = _InnerClass.used_by_outerclass

> The trick is you shouldn't write "._" as part of a reference. :-)

  But an outside code could do something along the lines of:

OuterClass::_InnerClass obj; // Assuming the compiler doesn't restrict this

obj.someFunction();

  The first line clearly breaks the privacy contract, but with the second
line it's not so obvious anymore. It's calling a public member of _InnerClass,
but it's intended to be "public" only for OuterClass (because _InnerClass is
part of the private implementation of OuterClass), not for anything else.

-- 
                                                          - Warp

Post a reply to this message

Warp wrote:
>   But an outside code could do something along the lines of:
> 
> OuterClass::_InnerClass obj; // Assuming the compiler doesn't restrict this
> 
> obj.someFunction();

That's correct. And no, the compiler doesn't restrict it. I don't know I've 
even heard of a source code tool that warns you about it, altho that would 
seem fairly easy to write, methinks.

Just FYI, the syntax for that would be
   obj = OuterClass._InnerClass()
   obj.someFunction()

OuterClass._InnerClass returns the class itself, since the class is just 
assigned as the value of the variable. Invoking that value with () does the 
equivalent of C++'s "new". Then you assign whatever the constructor returned 
to obj.  Depending on the existence of different functions inside the 
_InnerClass class, you get things like overridden "new" or overridden 
constructors.

And, technically, a constructor doesn't *have* to return an instance of the 
class you invoked, if you override "new" in the class and have it return 
something of a different class. So it's even uglier. :-) Just calling
   obj = OuterClass()
could actually wind up assigning an OuterClass._InnerClass instance to obj.
Handy for factory functions, tho.

>   The first line clearly breaks the privacy contract, but with the second
> line it's not so obvious anymore.

Correct.

On the other hand, it's the same result as if you did something like
obj = OuterClass::factory_method(...)
and factory_method returns an instance of _InnerClass. So it's not really 
something you could enforce there at the compiler level.  (As in, it would 
be hard to enforce at the obj.someFunction() call, but easier at the 
OuterClass._InnerClass access.)

I.e., I'm not sure I'd describe the second line as breaking the privacy 
contract. It's just using a value obtained by breaking the privacy contract. 
But that's just a matter of wording, really.

> It's calling a public member of _InnerClass,
> but it's intended to be "public" only for OuterClass 

Not necessarily. If OuterClass returns an instance of _InnerClass (like, if 
OuterClass is a collection and _InnerClass is an iterator over the 
collection) it might make sense.

> (because _InnerClass is
> part of the private implementation of OuterClass), not for anything else.

If OuterClass never returns instances of _InnerClass, yes, that would be a 
difficult violation of modularity to track down. It's certainly not the best 
way of doing things if you're worried about that sort of thing.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

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Darren New wrote:
> It's certainly not 
> the best way of doing things if you're worried about that sort of thing.

Um, "it" there means "Python's way of handling private variables", not 
"inner classes".  As in, naming conventions aren't the best way of handling 
private members if you're worried about someone violating the privacy.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Warp wrote:
>   And it's getting really tiresome and old that you act all innocent after
> a tirade of C++ bashing, 

Can you do me a favor, for the sake of future conversations?

Can you tell me what I said that you took to be "a tirade of C++ bashing"?

As far as I can see, I've been trying to be factual and honest. You started 
out using derogatory terms like "it's a kludge", and "that's BS", and 
referring to people as "self-taught hackers" and "use a fancy term instead 
of admitting their mistake" and "In Utopia, maybe" and the usual insulting 
hyperbole.

Where did I say anything derogatory about C++? I would like to know what I 
said about C++ that you took to be saying C++ is *bad*. Can you actually 
quote what I wrote that you took to be "C++ bashing", let alone a "tirade"?

As far as I can see, the conversation (once it got to be about modularity 
instead of minimalism) went something like
You: "Modularity is good. Breaking modularity is bad."
Me: "Yes. But everyone breaks modularity in different ways.
    CLOS breaks it by doing A
    C# and Java breaks it by doing B
    Python breaks it by doing C
    C++ breaks it by doing D
    I prefer B over D."
You: "D doesn't count. C++ doesn't break modularity."
Me: "Wild pointers."
You: "Doesn't count - not standard."
Me: "Memset"
You: "Doesn't count - non portable."
Me: "But it still happens."
You: "You're so mean, always bashing C++."

So, in all honestly, I'd really like to know where in the process I said 
something that "bashed" C++, rather than simply comparing its behavior with 
other languages and explaining (in detail) why I preferred the other mechanisms.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

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Warp wrote:
>   You can't access the private variable by address. Not according to the
> standard. 

http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1905.pdf
Section 3.9 paragraph 2, page 60 sheet 74.

#define N sizeof(T)
char buf[N];
T obj ; // obj initialized to its original value
std::memcpy(buf, &obj, N); // between these two calls to std::memcpy,
                            // obj might be modified
std::memcpy(&obj, buf, N); // at this point, each subobject of obj of scalar 
type
// holds its original value


Yet I'm sure at this point that there will be some reason this doesn't count 
as violating modularity. Will it be that it's only a draft of the standard? 
Will it be that it's only true of POD types? Will it be because it only says 
it works for reading and writing all the private variables at once?

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

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Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
> >   You can't access the private variable by address. Not according to the
> > standard. 

> http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1905.pdf
> Section 3.9 paragraph 2, page 60 sheet 74.

> #define N sizeof(T)
> char buf[N];
> T obj ; // obj initialized to its original value
> std::memcpy(buf, &obj, N); // between these two calls to std::memcpy,
>                             // obj might be modified
> std::memcpy(&obj, buf, N); // at this point, each subobject of obj of scalar 
> type
> // holds its original value


> Yet I'm sure at this point that there will be some reason this doesn't count 
> as violating modularity. Will it be that it's only a draft of the standard? 
> Will it be that it's only true of POD types? Will it be because it only says 
> it works for reading and writing all the private variables at once?

  By the same logic this would also "break modularity":

T obj;
T obj2 = obj;

  All the data in obj is copied to obj2. This includes all the private data.

  However, the memcpy() version *is* breaking modularity because, as the
text says, it's guaranteed to work only if the object contains scalar
types. If you assume it does, you are breaking modularity.

-- 
                                                          - Warp

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Darren New <dne### [at] sanrrcom> wrote:
> Can you tell me what I said that you took to be "a tirade of C++ bashing"?

  A combination of concepts gave me the impression that you were
denigrating the way C++ does thing, while praising how other languages
do it better.

  Maybe you didn't use the word "unsafe" in a derogatory manner, but it
was easy to get the impression. When you said basically that it's not true
that C++ enforces modularity, and proceeded to "demonstrate" that by
trying to give examples of how you can circumvent C++'s semantics by
using low-level pointer casting and arithmetic, it gave the impression
that you were denigrating C++ for trying to do something and failing
miserably. This impression was emphasized by you at the same time telling
how you prefer how other languages do it "right" by having explicit support
for breaking the module interface boundaries, while in C++ you have to
resort to non-standard hacks to do the same. Also your arguments why
someone would even want to break the interface boundaries was not completely
convincing to me. (Your only argument seemed to be "reflection", and my
only experience on it is with Objective-C, where it's done without really
accessing private members from the outside, at least as far as I have had
to deal with it.) When you wrote that C++ is the only unsafe OO language
you know of, it sounded like you were bragging how *all* other OO languages
are better than C++, which gives the impression that you are telling that
C++ is the worst possible OO language in existence.

  I apologize if I overreacted.

-- 
                                                          - Warp

Post a reply to this message

Warp wrote:
>   By the same logic this would also "break modularity":
> 
> T obj;
> T obj2 = obj;

Not really. operator= is declared in T.

>   All the data in obj is copied to obj2. This includes all the private data.

Only if you say that's how you want it to work.

>   However, the memcpy() version *is* breaking modularity because, as the
> text says, it's guaranteed to work only if the object contains scalar
> types. If you assume it does, you are breaking modularity.

You don't have to assume it does. You can read the header file and see it 
does. :-)

In any case, yes, you're breaking modularity. That's what we're saying, yes? 
Accessing private variables without the permission of the class breaks 
modularity?  Accessing private variables by address in a 
standards-conforming way breaks modularity. Given that you're agreeing with 
me, I'm not sure what the "however" in your sentence is supposed to imply.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Warp wrote:
> Darren New <dne### [at] sanrrcom> wrote:
>> Can you tell me what I said that you took to be "a tirade of C++ bashing"?
> 
>   A combination of concepts gave me the impression that you were
> denigrating the way C++ does thing, while praising how other languages
> do it better.

OK. As I said, I simply said I prefer how the other languages break 
modularity instead, and then I listed the reasons. "Bashing" to me implies 
denegrating it either by lying about its capabilities or saying it's bad for 
no reason or using abusive language or something like that, yes?

And yes, I was saying I prefer how other languages do it to how C++ does it, 
and I listed the reasons why. We all know why C++ does things the way it 
does, and the benefits that provides to the programmer. That doesn't make it 
"C++ bashing." If anything, the bashing was of Java in the original post.

>   Maybe you didn't use the word "unsafe" in a derogatory manner, but it
> was easy to get the impression.

I think you're oversensitive about that. I don't like unsafe languages for 
the reasons I've stated, but I don't know how saying that is "derogatory". I 
said "C is unsafe", I didn't say "C is a fucked up steaming hack pile of 
garbage whose inventors should be shot for being so stupid."  *That* is 
derogatory.

> When you said basically that it's not true
> that C++ enforces modularity, and proceeded to "demonstrate" that by
> trying to give examples of how you can circumvent C++'s semantics by
> using low-level pointer casting and arithmetic, it gave the impression
> that you were denigrating C++ for trying to do something and failing
> miserably.

OK. That wasn't the impression I was trying to convey. I was simply trying 
to point out that no unsafe language is truly modular, and the easier it is 
to find the unsafe operations, the easier it is to debug accidental breakage 
of modularity.

 > This impression was emphasized by you at the same time telling
> how you prefer how other languages do it "right" by having explicit support
> for breaking the module interface boundaries, while in C++ you have to
> resort to non-standard hacks to do the same.

You have to resort to non-standard hacks to *intentionally* break 
modularity, is what I said. And that there's two types of modularity involved.

> Also your arguments why
> someone would even want to break the interface boundaries was not completely
> convincing to me. (Your only argument seemed to be "reflection", and my
> only experience on it is with Objective-C, where it's done without really
> accessing private members from the outside, at least as far as I have had
> to deal with it.)

It doesn't happen really often, which is why I thought *you* were 
overreacting by calling CLOS a kludge OO system simply because you can break 
modularity by reading the source of the module. :-)

> When you wrote that C++ is the only unsafe OO language
> you know of, it sounded like you were bragging how *all* other OO languages
> are better than C++, which gives the impression that you are telling that
> C++ is the worst possible OO language in existence.

I said that because you challenged me to say which I'm talking about. By 
then, you were already convinced I had to be bashing C++ and I was trying to 
hide it after the fact. :-)

>   I apologize if I overreacted.

Apology accepted. I believe you did. I admit I've bashed C++ in the past in 
some ways, so it's not unreasonable, but I've been trying not to do that for 
quite some time now. It's primarily you teaching me about the power of it in 
conversations like this that has made me appreciate for what it is.

It's actually not that bad a language if it's the sort of language you need. 
I disagree with the design principles, and sometimes I explain why I 
disagree with them, but that's an opinion that everyone can feel free to 
decide for themselves. It's kind of funky how much power it can manage to 
build onto itself using what it comes with.

I'll try to be even *more* careful how I talk about things if you'll do me 
the favor that, when you get annoyed, you re-read without assuming I'm 
bashing and see if it still sounds like I'm "bashing."

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> In any case, yes, you're breaking modularity. That's what we're saying, yes? 
> Accessing private variables without the permission of the class breaks 
> modularity?  Accessing private variables by address in a 
> standards-conforming way breaks modularity. Given that you're agreeing with 
> me, I'm not sure what the "however" in your sentence is supposed to imply.

  The breaking of modularity in this case has little to do with accessing
private members, and more to do with bypassing the normal copy constructor
or assignment operator semantics through reinterpret-casting pointers.

  "a = b;" and "memcpy(&a, &b, sizeof(a));" might in fact produce almost,
if not exactly identical machine code by the compiler, if the class in
question only has scalar types as members (and doesn't define an assignment
operator the compiler cannot see at this point). Thus at machine code
level the two expressions might in fact be completely identical.

  With this I mean that with the memcpy() you are not accessing the private
members any more than you are with "a = b;". They are both copying the
state of the entire object to another instance. You could say that with
memcpy() you still don't know *what* you are copying (what type of members,
how they are padded inside the class, etc), only that you are copying
everything verbatim.

  The difference, and what makes the memcpy() version non-modular, is that
the memcpy() version bypasses the normal class assignment semantics and
instead goes to the "raw hardware level". If the class would need a more
complex copying semantics than a bit-by-bit copy, then the copy is broken.

  I understand your argument to be that memcpy() could be used in this
way to *access* the private members of the object. However, it can't,
not in a portable way anyways, because you still can't know the internal
structure the compiler has generated for the class, and you can't point
to individual private elements.

  Perhaps this could be compared to calling the CopyFile() function of
the Windows API: Even though it copies the entire contents of a file to
another file, I'm still not *accessing* the contents of the file with
that function in my program. I'm just telling the system to copy it.

-- 
                                                          - Warp

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Darren New <dne### [at] sanrrcom> wrote:
> OK. As I said, I simply said I prefer how the other languages break 
> modularity instead, and then I listed the reasons. "Bashing" to me implies 
> denegrating it either by lying about its capabilities or saying it's bad for 
> no reason or using abusive language or something like that, yes?

  I understand that "bashing" can also be used to describe overly negative
critique of something in a way that, while not telling any lies per se,
makes it sound a lot worse than it really is. Especially if the impact of
many of these negative things is exaggerated, and especifally if all this
is done on purpose.

  For example, in my "I hate Java" page I'm outright bashing Java because
I'm pointing everything that I consider negative about it, without pointing
out anything positive to compensate (although Java does have its positive
things as well). Someone who didn't know anything about Java could get a
rather biased impression of the language by reading that page alone. (Guess
twice if I care. ;) )

-- 
                                                          - Warp

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Warp wrote:
>   I understand that "bashing" can also be used to describe overly negative
> critique of something in a way that, while not telling any lies per se,
> makes it sound a lot worse than it really is. 

Fair enough. I thought we'd already talked to death the advantages of unsafe 
languages (primarily performance and control).

> Especially if the impact of
> many of these negative things is exaggerated, 

I think you underestimate how much of a problem some problems are for 
average programmers because you've become expert.  I still occasionally get 
questions from people who have been programming for decades who ask
   "How do I debug something when it stops crashing after I add a printf()?"

You yourself have posted C++ code with a quiz-like "what's wrong with this 
class".  Clearly it takes a fair amount of expertise to write correct C++ 
code, doesn't it?

I can write C code that doesn't have bugs due to the unsafeness, but it 
takes me much longer because I have to think a lot harder about the 
boundaries. It's also something that took years of experience to learn.

I also figured it wouldn't be taken to be "bashing C++" if I pointed out the 
equivalent flaws in the whole list of other languages we were talking about, 
which is what led me to believe you might be a bit oversensitive or 
oversensitized.

>   For example, in my "I hate Java" page I'm outright bashing Java because
> I'm pointing everything that I consider negative about it, without pointing
> out anything positive to compensate (although Java does have its positive
> things as well). Someone who didn't know anything about Java could get a
> rather biased impression of the language by reading that page alone. (Guess
> twice if I care. ;) )

There's nothing wrong IMO with a good bash so labeled. I don't think 
anyone's going to read a page labeled "I hate Java" and expect a balanced 
presentation, any more than they're going to go to apple.com to see the pros 
vs cons of apples vs windows, say. I even think something like the C++ FQA 
is a valuable service, bashing as it is. I wish there were pages like that 
for every language and tool.

I don't think it's a bash of any one language to say "no language strictly 
enforces modularity, they're all broken in various ways, and here they are: 
...."  I'm hoping it's not considered bashing Y to say "I like X better than 
Y because ..."  It's not like I started talking about the flaws I think are 
in the design of C++ that haven't anything to do with violating modularity, 
or that I argued you can't violate modularity in the other languages.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

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Warp wrote:
>   With this I mean that with the memcpy() you are not accessing the private
> members any more than you are with "a = b;".

I would disagree for the following reason:

Altho {a = b;} *might* do the same thing as memcpy(), the author of the 
class has the ability to make it do something different, or to declare 
operator= to be private, preventing it altogether.

memcpy() can not be "defended against" in that sense.

"Can I change the values of private variables without invoking a class 
method or friend function?"  "Yes."  I'd say that's breaking modularity.

I think at this point we each understand what the other is saying, and now 
we're just having an argument about whether to call it "really" unmodular or 
only "kinda" unmodular. :-)

> They are both copying the
> state of the entire object to another instance. You could say that with
> memcpy() you still don't know *what* you are copying (what type of members,
> how they are padded inside the class, etc), only that you are copying
> everything verbatim.

Note, too, that even in this case, if you change your pixel example to be 
HSV instead of RGB, the memcpy() approach still works for moving pixels 
around. :-)

>   The difference, and what makes the memcpy() version non-modular, is that
> the memcpy() version bypasses the normal class assignment semantics and
> instead goes to the "raw hardware level". If the class would need a more
> complex copying semantics than a bit-by-bit copy, then the copy is broken.

Sure. I'm just arguing that the ability to use memcpy() *is* non-modular. 
The fact that it breaks or is non-portable in some cases would not seem to 
counter that fact. It would just seem to say "it's a bad way of doing 
things." :-) Which we both agree with.

>   I understand your argument to be that memcpy() could be used in this
> way to *access* the private members of the object. However, it can't,
> not in a portable way anyways, because you still can't know the internal
> structure the compiler has generated for the class, and you can't point
> to individual private elements.

Agreed. Not that it's difficult to figure out. I can think of at least 3 
easy ways to figure out where individual variables are: 1) use a debugger, 
2) look at the generated asm code, 3) stick a friend function into the 
header that returns the offset of the private instance. None of those are 
particularly portable, except the last, assuming that adding a friend 
function declaration doesn't rearrange the actual structure members.

I agree it's a concern in CLOS that someone will read your source code and 
access the internals of your class by learning the names of private 
variables and then you'll have to support it. I also contend it's about the 
same level of concern that someone will look at your header file, see it's 
POD, and write code that uses memcpy() to move POD-structs around (perhaps 
to different address spaces or into files or something), and you'll wind up 
having to support that.  Neither is really common enough to worry about, and 
both are trivial to avoid if you can change the module you're talking about 
or avoid the need to do that altogether in the caller.

>   Perhaps this could be compared to calling the CopyFile() function of
> the Windows API: Even though it copies the entire contents of a file to
> another file, I'm still not *accessing* the contents of the file with
> that function in my program. I'm just telling the system to copy it.

Sure. And my comparison would be that "Anything you can call CopyFile() on, 
you can open and read and write, possibly messing up the program that uses 
the file, or possibly for the purpose of bypassing DRM."

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

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Warp wrote:
>   I understand that "bashing" can also be used to describe overly negative
> critique of something 

Or, to just phrase it a different way, I've been actively and consciously 
attempting not to say bad things about C++ and to ensure whenever I point 
out a limitation I also point out the equivalent limitation in other 
languages. Yet you continue to fall back on "you're bashing C++ to annoy 
me", which is kind of discouraging.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Darren New wrote:
> I agree it's a concern in CLOS that someone will read your source code 

Or, to phrase it a bit differently, I'll agree that using memset() or 
memcpy() to get to the entire instance opaquely *feels* qualitatively 
different than the sorts of access CLOS or Python allows.

On the other hand, it seems kind of similar to the sorts of things 
reflection allows.

Even in Python, I think there's two kinds of accesses:
    x = myinstance._myprivatevar
vs
    "iterate over all public and private variables of this instance
     and do XYZ with them."
They feel qualitatively different, with the latter feeling more like
reflection and the former feeling more like bad news, even though they
both stem from precisely the same language rules.



As an example you might be able to relate to, to see what I'm talking about, 
consider http://www.boost.org/doc/libs/1_38_0/libs/serialization/doc/index.html

Look at the "class gps_position" example. It has a pair of routines named 
"serialize" each of which lists the exact same variables in the routine as 
are in the class. With a reflection library, adding this sort of 
serialization would be done by having a mix-in multi-inheritance routine, 
and you wouldn't need to code that sort of body at all. Of course, there 
would likely be routines like "serialize everything" and "serialize all 
public members", as well as routines like "serialize everything but X and Y, 
and when you load back in from the archive, invoke fix_up() on the loaded 
instance to fix X and Y." So lots of uses of this sort of thing are done 
from within the class, just taking advantage of the fact that you *already* 
listed the names and types of the instance variables, so why do it again?

Yeah, you can use it to get to the insides of classes from outsides, but you 
kind of want that for your IDE and your debugger. :-) It's a lot of power, 
and IME not a whole lot of misuse.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

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Darren New <dne### [at] sanrrcom> wrote:
> Or, to just phrase it a different way, I've been actively and consciously 
> attempting not to say bad things about C++ and to ensure whenever I point 
> out a limitation I also point out the equivalent limitation in other 
> languages. Yet you continue to fall back on "you're bashing C++ to annoy 
> me", which is kind of discouraging.

  I'll try to be less paranoid next time.

-- 
                                                          - Warp

Post a reply to this message

Warp wrote:
>   I'll try to be less paranoid next time.

Thank you. I appreciate it.  In return, feel free to say something early on 
if it sounds like I'm not making the effort. :-)

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Darren New <dne### [at] sanrrcom> wrote:
> Warp wrote:
> >   I'll try to be less paranoid next time.
>
> Thank you. I appreciate it.  In return, feel free to say something early on
> if it sounds like I'm not making the effort. :-)

whoa!  A lot of kicks, punches and bruises later and you almost feel in love...
:P

Post a reply to this message

nemesis wrote:
> whoa!  A lot of kicks, punches and bruises later and you almost feel in love...

I'm not offended by anything Warp has said. He's a smart and insightful guy 
with lots of knowledge. I learn enough from him I want to stay on his good 
side. Occasionally his conversations style is annoying, but I'm pretty sure 
mine is moreso. :-)

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

Post a reply to this message

Darren New wrote:

> http://vijaymathew.wordpress.com/2009/03/13/dangerous-designs/

Why write

   (define (addn n) (lambda (k) (+ n k)))

when you can just say

   addn n = (+n)

? ;-)

Seriously though, adding completely new features to a system not 
designed to support them is not an easy thing to do. This is not news. I 
do, however, agree that a simple design that is widely powerful is 
better than a huge raft of special-purpose rules for specific situations.

(This is one of the reasons why Haskell's ever-expanding set of features 
worries me. If people need all these extra features, doesn't that kind 
of indicate that the language is broken?)

Post a reply to this message

Warp wrote:

> "The argument is that, using a very small number of rules for forming
> expressions and with a minimal syntax it is possible to support all
> possible programming paradigms. For instance, if the language has
> support for higher-order functions, closures and dynamic typing, we
> can implement object oriented programming without special language
> level syntactic support. Tail-call optimization elude the need for
> special looping constructs."
> 
> sounds like you could argue in favor of languages like brainfuck which
> have a minimal set of instructions, yet are still Turing-complete.
> 
>   Eg. just because tail recursion is enough to perform any kind of
> looping construct doesn't necessarily mean that special looping constructs
> wouldn't be a useful tool.

If a language is "powerful enough", you can create the abstractions you 
need from within the language and use that. If the language is not 
powerful enough, the things you need must be hard-coded into the 
language, which is less flexible.

On the other hand, a compiler can take advantage of the specific 
features of a specific language, but can't easily take advantage of the 
properties of some custom abstraction that you designed yourself. 
(Although some languages allow the programmer to specify compile-time 
transformations that go some of the way.)

Post a reply to this message

Invisible wrote:
> Darren New wrote:
> 
>> http://vijaymathew.wordpress.com/2009/03/13/dangerous-designs/
> 
> Why write
> 
>   (define (addn n) (lambda (k) (+ n k)))
> 
> when you can just say
> 
>   addn n = (+n)

Shouldn't that be addn n = (n+) ?

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

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Darren New wrote:
> Invisible wrote:
>> Why write
>>
>>   (define (addn n) (lambda (k) (+ n k)))
>>
>> when you can just say
>>
>>   addn n = (+n)
> 
> Shouldn't that be addn n = (n+) ?

It doesn't matter. Addition is usually a commutative operation.

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I see you're back! :D

Invisible escreveu:
> Darren New wrote:
> 
>> http://vijaymathew.wordpress.com/2009/03/13/dangerous-designs/
> 
> Why write
> 
>   (define (addn n) (lambda (k) (+ n k)))
> 
> when you can just say
> 
>   addn n = (+n)
> 
> ? ;-)

Because in plain Scheme you can't?

> (This is one of the reasons why Haskell's ever-expanding set of features 
> worries me. If people need all these extra features, doesn't that kind 
> of indicate that the language is broken?)

If I'm not wrong, core Haskell is about as clean and simple as plain 
Scheme, both based on lambda calculus.  Building upon solid, flexible 
and simple infrastructure is not a bad idea.

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Invisible <voi### [at] devnull> wrote:
> > Shouldn't that be addn n = (n+) ?

> It doesn't matter. Addition is usually a commutative operation.

  Unless you are using the + operator to, for example, concatenate strings...

-- 
                                                          - Warp

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>>> Shouldn't that be addn n = (n+) ?
> 
>> It doesn't matter. Addition is usually a commutative operation.
> 
>   Unless you are using the + operator to, for example, concatenate strings...

Sure. In that case, it makes a difference - and so you'd better decide 
which one you actually meant. But remember, Haskell's string concat 
operator is (++), not (+).

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nemesis wrote:
> I see you're back! :D

You can't see my back. It's invisible. ;-)

>> Why write
>>
>>   (define (addn n) (lambda (k) (+ n k)))
>>
>> when you can just say
>>
>>   addn n = (+n)
>>
>> ? ;-)
> 
> Because in plain Scheme you can't?

I know that. ;-) I'm just being a Haskell whore, as usual.

>> (This is one of the reasons why Haskell's ever-expanding set of 
>> features worries me. If people need all these extra features, doesn't 
>> that kind of indicate that the language is broken?)
> 
> If I'm not wrong, core Haskell is about as clean and simple as plain 
> Scheme, both based on lambda calculus.  Building upon solid, flexible 
> and simple infrastructure is not a bad idea.

Sure. But taking a solid, flexible and simple infrastructure and making 
it complex and convoluted isn't such a hot idea.

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Invisible <voi### [at] devnull> wrote:
> Sure. In that case, it makes a difference - and so you'd better decide 
> which one you actually meant. But remember, Haskell's string concat 
> operator is (++), not (+).

  Well, better example: If the operator is * and the elements are matrices.

-- 
                                                          - Warp

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Warp wrote:
> Invisible <voi### [at] devnull> wrote:
>> Sure. In that case, it makes a difference - and so you'd better decide 
>> which one you actually meant. But remember, Haskell's string concat 
>> operator is (++), not (+).
> 
>   Well, better example: If the operator is * and the elements are matrices.

Yes. In that case, you'd better be really clear about which way you 
actually meant.

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Invisible wrote:
> Sure. But taking a solid, flexible and simple infrastructure and making 
> it complex and convoluted isn't such a hot idea.

The secret is to have something in the infrastructure that lets you hide the 
convoluted complexity, whether that be LISP macros or Tcl upvar or C++ 
templates. Otherwise, you get Java.

-- 
   Darren New, San Diego CA, USA (PST)
   My fortune cookie said, "You will soon be
   unable to read this, even at arm's length."

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Invisible escreveu:
> nemesis wrote:
>> If I'm not wrong, core Haskell is about as clean and simple as plain 
>> Scheme, both based on lambda calculus.  Building upon solid, flexible 
>> and simple infrastructure is not a bad idea.
> 
> Sure. But taking a solid, flexible and simple infrastructure and making 
> it complex and convoluted isn't such a hot idea.

By simple of course we mean things that twist and bend the minds of 
common, mortal programmers.  We're just abstracting that a step further. ;)

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