Article of interest: Python pros/cons for the enterprise

[Nicola Musatti]

On Feb 22, 12:07 pm, Paul Rubin <http://phr...@NOSPAM.invalid> wrote:
> Nicola Musatti <nicola.musa... at gmail.com> 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.

Cheers,
Nicola Musatti