Re: Some errors in MIT's intro C++ course

From:

Juha Nieminen <nospam@thanks.invalid>

Newsgroups:

comp.lang.c++,comp.programming

Date:

10 Sep 2010 19:50:03 GMT

Message-ID:

<4c8a8beb$0$12263$7b1e8fa0@news.nbl.fi>

In comp.lang.c++ Christian Hackl <hacki@sbox.tugraz.at> wrote:

Juha Nieminen ha scritto:

In comp.lang.c++ James Kanze <james.kanze@gmail.com> wrote:

To make an array you write: std::vector<element_type> v(size);
To access to the vector you write: v.at(index)

Why the at? That's an advanced feature, for the special (and
rare) cases where you want an exception on a bounds error,
instead of a crash.

Since when has the safer variant been the "advanced feature", while the
variant which causes UB when misused is the one suitable for beginners?

For beginners it won't really make a difference.

It makes a huge difference if the program tells the user "hey, you
accessed this vector out of boundaries, bad, bad" rather than behaving
erratically for unknown reasons.

In practice, in both
cases their program will safely crash

  In which system does accessing a vector out of boundaries "safely crash"
for sure?

  In most systems I know of it *might* crash, but it might also corrupt
some unrelated object/variable, causing erratic behavior which can be
really hard to debug.

  Using at() avoids that.