On Fri, 22 Feb 2008 04:48:28 -0800, Nicola Musatti wrote:
> On Feb 22, 12:07 pm, Paul Rubin <http://[EMAIL PROTECTED]> wrote:
>> Nicola Musatti <[EMAIL PROTECTED]> writes:
>> > In C++ memory is just another resource which you can handle just like
>> > any other one, possibly using RAII.
>>
>> Ok, I'll bite. Here's a straightforward Python expression:
>>
>> a = [f(x) + g(y) for x,y in izip(m1, m2) if h(x,y).frob() == 7]
>>
>> Consider how many intermediate objects are being allocated in figuring
>> out that listcomp. Do you REALLY want to manage all the deallocation
>> with something like RAII?
>
>
> What makes you think that a translation of a similar expression would
> involve explicit dynamic allocation at all? Barring bugs, here's an
> equivalent example:
>
> #include <iostream>
> #include <map>
> #include <vector>
>
> int f(int n) { return n * 2; }
> int g(int n) { return ( n * 2 ) + 1; }
>
> std::map<int, int> izip(int i, int j) {
> std::map<int, int> m;
> m[i] = j;
> m[j] = i;
> return m;
> }
>
> class A {
> int i, j;
> public:
> A(int ii, int jj) : i(ii), j(jj) {}
> int frob() { return i + j; }
> };
>
> A h(int i, int j) { return A(i, j); }
>
> int main() {
> int m1 = 3;
> int m2 = 4;
> std::vector<int> a;
> std::map<int, int> m = izip(m1, m2);
> for ( std::map<int,int>::iterator i = m.begin(); i != m.end(); ++i )
> {
> if ( h(i->first, i->second).frob() == 7 )
> a.push_back(f(i->first) + g(i->second));
> }
> for ( std::vector<int>::iterator i = a.begin(); i != a.end(); ++i )
> std::cout << *i << '\n';
> }
>
> As you can see the standard library takes care of all memory
> management.
Aaah, that's much nicer and easier to understand than the list
comprehension. After this great example I'll switch to C++. ;-)
But somehow you still manage memory by writing in a style that favors
value types.
SCNR,
Marc 'BlackJack' Rintsch
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