Re: Brian Kernighan, maybe I'm not worthy, maybe I'm scum

On Dec 31 2007, 10:00 pm, Richard Heathfield <r...@xxxxxxxxxxxxxxx>
wrote:
spinoza1111said:

I have an idea for reducing the cyberbullying at this ng which I've
also used at humanities.lit.authors.shakespeare.

It is "The Spinoza Challenge".

I will take a test on a programming topic without special preparation
and closed book, and report my score, along with information as to my
overall familiarity with the tested platform, language or topic.

My first Spinoza Challenge: beat my score: I just took the C++ test
that is available on Spark Notes at
http://www.sparknotes.com/cs/c++fundamentals/review/quiz.htmland
received 76%.

I have no particular comment to make on question 1, although I wouldn't
have worded the question like that.

Question 2 is unfortunate, since it has two correct answers; although it's
obvious which one is wanted, another of the answers is perfectly
defensible. Neither is exclusively correct.

Neither were meant to be: cf. "generally"

Question 3 is trivial.

Question 4 is badly worded but one can get the gist easily enough. Strictly
speaking, the assignment operator - *provided that it is not overloaded to
do something else* - evaluates the right hand operand and copies the value
into the object specified by the left hand operand.

I think we can assume ceteris paribus as to the possibility of
overloaded redefinition of operators


Question 5 is broken. None of the specified types guarantees the necessary
precision for dealing with twenty decimal digits. The long double type
only guarantees ten. One could reasonably argue that any of the integer
types mentioned gives an adequate basis for developing a bignum library
that could give the required precision.

Bad flaw, I agree. Still, life's unfair. Do you suggest abandoning the
challenge or finding new tests? I can search for better tests if you
like. I'd say your analyses exhibit fairly good qualifications were it
not for your analysis of question 6, which I do not accept.

Question 6 is broken. None of the supplied answers gives the required
output, which is:

a c b d

(A) will give a\t\nb\td
(B) will give some output dependent on the (unsupplied) values of the
objects given in the expression.
(C) will give acb\nd
(D) will give ab\nc\td

In the cases of A, C, and D, the backslashes shown here do not introduce
escape sequences (which would in any case break their conformance to the
requirement), but literally part of the output, as they are themselves
escaped.

You may be right. This question may be trash. Still, to be fair to
all, we need to all accept these tests as final in order to be able to
compare scores, which are not precise measures of qualifications, but
even in their imprecision are better than random character and
professional assassination.

Question 7 is trivial.

Question 8 is broken. All of the suggested answers except A exhibit
undefined behviour, and answer A modifies the value of x. There is no
correct answer.

(A) x++;
(B) x += x--;
(C) x = x++;
(D) x = --x + 1;

The correct answer is D, and neither it nor any question exhibits
undefined behavior in C++, or in usable C compilers.

A adds one to the value of x and returns the value before the
increment to thin air. x is changed.

In B, x is stacked and then decremented in place. The stack copy is
then added to x. The decrement happens BEFORE the assignment (simple
operator precedence). Therefore x is set to (x-1)+x, where x is the
starter value. The behavior is NOT undefined, as far as I can tell.
Please inform me of why you believe otherwise. We can safely assume x
is long or int. x is changed. If someone comes up with a value, int or
float or double in which it doesn't change, this still makes this the
wrong answer because in D (see below) x is unchanged.

By the same reasoning as for B, x is set in C to (x+1)+x.

D decrements x, stacks it, adds one, and then replaces decremented x
by (x-1)+1. No change except perhaps for pathological cases near the
end of floating point precision.

Richard, am I missing something? The value is well-defined as long as
you commonsensically assume x to be int. The BEHAVIOR is well-defined,
period.


Question 9 is trivial.

Question 10 fails to account for pointer comparison, but is otherwise
trivial.

In C and C++, pointers are integers and as such compareable


Questions 11, 12, and 13 are trivial.

Question 14 is ambiguous - it depends on whether you consider 'between' to
be inclusive. I don't, so I might disagree with the marker over which
answer should be considered correct.

Question 14 does NOT depend on whether the English word "between" is
inclusive. In ordinary speech it is used both ways! But the competing
answer uses an OR (hope you noticed) and the best answer is A. The
ONLY answer is the BEST answer.

Question 15 is trivial.

Question 16 is trivial if you discount the possibility that the break
appears inside a switch.

Questions 17 and 18 are trivial, but 18 is very badly worded.

Questions 19, 20, and 21 are trivial.

Question 22 is incorrect. sqrt is declared in <math.h> but only a complete
bozo would define it there.

If we MUST use terms like "bozo", only a complete bozo would use
"define" when he means use, dear Richard. The correct answer, I
believe, is #include. Do inform me why the question is "incorrect".


Questions 23-27 are trivial.

Question 28 has no good answer. There's no reason why you can't write a
linked list class (although there's no point, because there's one in the
STL). Nor is there any reason why you couldn't use structs to implement a
linked list. Nor is there any reason why you can't construct a linked list
that can hold only a single type. Nor is there any point in constructing a
linked list that can only have a fixed number of elements.

Question 29 has no correct answer. Arrays don't hold types. They *have*
types, but they are aggregate types that can store multiple *objects* of a
given type. If we agree that that's kinda what the guy meant only he
didn't say it very well, we must discount (A) as being incorrect (because
they can hold complicated types such as user-defined types). We must also
discount (B) because arrays can't hold function types (although they /can/
hold function pointer types). And we must discount (C) for the same reason
as (B).

Gee, is a function a type? What on earth would it mean to write a
function (define it, that is) and then declare an instance of it?

C and C++ functions are not first class objects.


Questions 30 and 31 are trivial.

Question 32 has no correct answer.

No, creating a struct is similar to creating a class. C sucked because
you could not hide functionality inside structs in most compilers (you
can do so in C Sharp and Visual Basic). structs didn't know it, but
they wanted to be objects.

Questions 33-43 are trivial.

Question 44 has no clearly correct answer. (A) is wrong because it doesn't
access the base class function. (B) is wrong because it uses a class name
in an object context. (C) is wrong unless the code exists within the class
of which the function is a member.

B is the best answer of a bad lot. They forgot to tell you that
statics are qualified with the name of the class, and not an instance.
I do not speak with C++ honcho authority but as a compiler and
language designer who asked himself, while taking the test, how a
sensible language would expose a static code-only function, that uses
no instance variables. Sure, old VB-4 forced you to instantiate to get
an effectively "shared" function, but that's because VB-4 sucked.


Questions 45-47 are trivial.

Questions 48-49 seem to use the word "composition" in a way I'm not
familiar with. I think of the term as applying to the moving of a

Nor I. I think I hosed them. Here, you'd have to read the Spark Notes
notes to prep, and these notes aren't written by geniuses. They are
written by high school teachers and graduate students and are nothing
more than study aids.

subexpression evaluation into an object that stores the subexpression to
make subsequent evaluation of the whole expression simpler and quicker. It
is not obvious that the suggested answers have anything to do with this!
This may simply be because I'm not as up on C++ as the author of the quiz.
Given the brokenness of the rest of it, however, I do not find that
possibility to be terribly likely.

Question 50 is trivial.

I didn't give answers to the ones I thought had no correct answer. I scored
80% (i.e. 40 out of 50).

--
Richard Heathfield <http://www.cpax.org.uk>
Email: -http://www. +rjh@
Google users: <http://www.cpax.org.uk/prg/writings/googly.php>
"Usenet is a strange place" - dmr 29 July 1999

Excellent score, and thanks for your comments.

I think that IF you have used C++ professionally in the past for any
significant length of time, and scored only 4 points more than a
person who's only occasionally maintained C++, and who now only uses C
rarely, you might want to apologize at this time for the many comments
you have made about my professional qualifications. When I posted in
2003, you took a vanishingly small number of data points and blew them
out of proportion. I'm not going to do that with the questions you got
wrong.

By the same ethics, logic, logical ethics, and ethical logic that you
shouldn't go about character and professional assasination based on a
few lines of code and many stylistic tics of your own, your failure to
score high on this test should not be interpreted as meaning that
you're not the Expert you want to be. You are...until you incite mob
action and enable cyberbullying, because being a professional is more
about collegiality and less about examinations and picoseconds.

I ask you in future to emulate my style in my comment on your comment
on question 6. I believe that the prefix and postfix increment and
decrement operators have, or damned well better have, an order of
execution relative to the precedence of assignment. If "modern" C
programmers override this in some way, say by overloading, then they
are idiots.

But, you're not an idiot. I suggest that your score and your mostly
intelligent remarks make you anything but, and I simply ask in future
that you might want to be, not more humble, but more collegial.
.

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