Re: For each in C++?

From:
SG <s.gesemann@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Thu, 26 Feb 2009 14:18:25 -0800 (PST)
Message-ID:
<16b2c31a-8213-4dfb-a62e-409cd4c44517@41g2000yqf.googlegroups.com>
On 26 Feb., 22:38, "mlt" <a...@asd.com> wrote:

Ok this compiles and gives the correct results:

std::vector<int> U;
U.push_back(1);
U.push_back(2);
U.push_back(3);

  for each(int u in U) {
   std::cout << "u = " << u << std::endl;
  }

so "For each" actually is working in C++ like in java.


No, it isn't. And I won't. It will be much better. :-)

In future C++ you will be able to write

  for (int u : U) {
    std::cout << "u = " << u << std::endl;
  }

after including

  #include <for>

and as for how it compares to the java version: Java uses runtime
polymorphism for its iterators (since interfaces are the only
abstraction mechanism). C++ (or more specifically its standard
library) uses compile-time polymorphism for iterators. So, such a for-
each loop would work without an abstract base_iterator class. Another
way of saying the same thing is: In C++ you don't need an extra level
of indirection for iterating over some sequence.

Anyhow, this kind of "range loop" is currently not yet available (at
least not officially in non-experimental compilers -- as far as I
know)

Cheers!
SG

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