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What The ... ?

Question #24 in the otherwise quite reasonable C/C++ programming quiz at Cprogramming.com is as follows:

C is to C++ as 1 is to

a) What the heck? b) 2 c) 10

I think I have a new favourite interview question.

Anyway, have a guess what they give as an answer.

That’s right, b).

Apparently they think C is almost a strict subset of C++, in exactly the same way that 1 is almost a strict subset of 2.

It seems perfectly clear to me. You just need to go back to definitions.

What is C++? The Jargon File defines it as “Designed by Bjarne Stroustrup of AT&T Bell Labs as a successor to C. “

What is the number 2? Peano defined it as the successor to 1.

Ergo, Cis to C++ as 1 is to 2.

Q.E.D.

Do I get the job?

Ergo, C is to C++ as 1 is to 2.

Nicely done, except it probably should be the other way around. C99 is the most recent standardisation of C, dating back to 1999 (obviously). C++ was ratified as a standard in 1998.

Hence, C : C++ :: 2 : 1

And don’t call us, we’ll call you.

I think you just treat C as a regular variable, which means the expression C++ evaluates to 2. (You would of course soundly thrash any programmer who defined a variable using a capital letter.)

By this incremental reasoning, answer (c) is also correct, since any computer geek worth hiring looks at “10” and says “two.”

I think you just treat C as a regular variable, which means the expression C++ evaluates to 2.

No it doesn’t! If C is 1, then C++ evaluates to 1 also. ++C evaluates to 2.

I’m sorry, the position has been filled!

I agree that in the expression “C++,” if C is referenced, it returns the value 1 before incrementing C. But the entire expression evaluates to 2; else the following would never end:

for (C=1; C<=10; C++) { … }

Another way to say it: What’s the output of this?

int main() { int C = 1; while (C++ < 3) { printf(“%d\n”, C); } return 0; }

I’d take a leaf from the new series of Doctor Who, where they occasionally travel to the year five billion when numbers are augmented by other symbols – so the episode The End Of The World happens in the year 5.5/Apple/26. So I’d say that C++ is a partial superset of C with some incompatibilities, and therefore C is to C++ as 1 is to 1.943turnip7442gorilla04.

Do I win?

Sorry folks, but unlike you nerds, computers think in BINARY, not decimal. The binary representation for what you call “2” is “10”. So the correct answer is c) “10”.