}

}

On Sat, 14 Jan 2006, H. wrote:
> So I'm trying to get my head around exactly what a "closure" is. I've
> read what SICP says about closures via all of the references listed in
> the index. I understand the general concept of closures, but not the
> full implications.
> Part of my problem is that I have a lot of other
> terms running through my head from other languages (namely, JavaScript,
> Java, C++), and they seem to be getting in the way of understanding,
> instead of facilitating it!

}

}
> At first, I kind of thought of a closure as a block of code with its
> own scope.

> Then I read the wikipedia definition of closure, and it said
> that closures store information across function calls, so I thought of
> static variables in these blocks of code.

> Recently I read a closure was a "generic representation of a callback"

On Sun, 15 Jan 2006, Kjetil S. Matheussen wrote:
> closure* foo(int n){
>  closure* ret=calloc(1,sizeof(closure));
>  closure->func=innerfunction;
>  closure->n=n;
>  return closure;
> }

On Sun, 15 Jan 2006, Kjetil S. Matheussen wrote:
> On Sat, 14 Jan 2006, H. wrote:

>> So I'm trying to get my head around exactly what a "closure" is. I've
>> read what SICP says about closures via all of the references listed in
>> the index. I understand the general concept of closures, but not the
>> full implications.
>> Part of my problem is that I have a lot of other
>> terms running through my head from other languages (namely, JavaScript,
>> Java, C++), and they seem to be getting in the way of understanding,
>> instead of facilitating it!

> Well, in Java and C++, an object is some kind of lame closure. If you have
> closures in your languages, you probably can make objects as well.

> By the way, according to this page: http://www.paulgraham.com/icad.html ,
> javascript do support closures:

> function foo(n) {
>  return function (i) {
>           return n += i } }

> ...which in scheme is:

> (define (foo n)
>   (lambda (i)
>      (+ i n)))

On Sun, 15 Jan 2006, Kjetil S. Matheussen wrote:
> On Sat, 14 Jan 2006, H. wrote:

>> So I'm trying to get my head around exactly what a "closure" is. I've
>> read what SICP says about closures via all of the references listed in
>> the index. I understand the general concept of closures, but not the
>> full implications.
>> Part of my problem is that I have a lot of other
>> terms running through my head from other languages (namely, JavaScript,
>> Java, C++), and they seem to be getting in the way of understanding,
>> instead of facilitating it!

> Well, in Java and C++, an object is some kind of lame closure. If you have
> closures in your languages, you probably can make objects as well.

> By the way, according to this page: http://www.paulgraham.com/icad.html ,
> javascript do support closures:

> function foo(n) {
>  return function (i) {
>           return n += i } }

> ...which in scheme is:

> (define (foo n)
>   (lambda (i)
>      (+ i n)))

> In C, you could make a manual closure by doing something like this:

> static int innerfunction(closure *c,int i){
>   return c->n+i:
> }

> closure* foo(int n){
>  closure* ret=calloc(1,sizeof(closure));
>  closure->func=innerfunction;
>  closure->n=n;
>  return closure;
> }

}closure;

}

}

> In C, you could make a manual closure by doing something like this:

> static int innerfunction(closure *c,int i){
>     return c->n+i:
> }

> closure* foo(int n){
>    closure* ret=calloc(1,sizeof(closure));
>    closure->func=innerfunction;
>    closure->n=n;
>    return closure;
> }

"H." <hbe...@gmail.com> writes:

> [totalSideQuery]
> Do you happen to know if any implementation details changed between C
> and C++ that address closure issues ? I would think "no" because C is a
> subset of C++, and I would think "yes" because C++ is object-oriented
> and C is not.[/totalSideQuery]

};

> Not especially.  Objects help, and in C++ one can overload the
> function-calling operator.

> class adder {
>     int i;
> public:
>     adder(int n): i(n) {}
>     operator()(int n) {return n+i;}
> };

> ...

> adder plus_7(7);

> std::cout << plus_7(42) << std::endl << plus_7(18) << std::endl;

> Still clumsy compared to something that really has closures like Lisp,
> ECMAscript, etc.

H. wrote:
>>Not especially.  Objects help, and in C++ one can overload the
>>function-calling operator.

>>class adder {
>>    int i;
>>public:
>>    adder(int n): i(n) {}
>>    operator()(int n) {return n+i;}
>>};

>>...

>>adder plus_7(7);

>>std::cout << plus_7(42) << std::endl << plus_7(18) << std::endl;

>>Still clumsy compared to something that really has closures like Lisp,
>>ECMAscript, etc.

> When I try to compile this, I get an "ISO C++ forbids declaration of
> 'operator()' with no type" error.

> It seems like a good example I'd like to play around with more, if it's
> a valid one and I can get it to work.

"H." <hbe...@gmail.com> writes:

> When I try to compile this, I get an "ISO C++ forbids declaration of
> 'operator()' with no type" error.

> It seems like a good example I'd like to play around with more, if
> it's a valid one and I can get it to work.