c:\console.cpp(113) : error C2039: 'type' : is not a member of 'print<T>' with [T=tl<293,tl<283,tl<281,tl<277,tl<271,tl<269,tl<263,tl<257,tl<251,tl<241,tl<239,tl<233,tl<229,tl<227,tl<223,tl<211,tl<199,tl<197,tl<193,tl<191,tl<181,tl<179,tl<173,tl<167,tl<163,tl<157,tl<151,tl<149,tl<139,tl<137,tl<131,tl<127,tl<113,tl<109,tl<107,tl<103,tl<101,tl<97,tl<89,tl<83,tl<79,tl<73,tl<71,tl<67,tl<61,tl<59,tl<53,tl<47,tl<43,tl<41,tl<37,tl<31,tl<29,tl<23,tl<19,tl<17,tl<13,tl<11,tl<7,tl<5,tl<3,tl<2,tl<>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>]
> You wouldn't pass, because you didn't read the specs!
> "prints the numbers from 1 to 100." -- you printed 0-100! ;-)
This is specifically addressed in the "Exit Portability" section:
"1. It starts at 0 instead of 1. This is just to make the output more readable by having the number encoded in the template argument (T0, T1, T2, etc) map directly to its FizzBuzz representation. If you want a strict version of FizzBuzz, just change the template specialization to terminate on '1' and return a vector<int_<1> > instead."
That's not actually the precompiler. The "precompiler" in C++ is the pre-processor, which just does straightforward text substitution. Template metaprogramming uses (abuses) the compiler itself. Templates in C++ are Turing Complete: http://netvor.sk/~umage/docs/3rdparty/C++%20Templates%20are%...
oh, sorry for the terminology glitch. Know about turing completeness, have used it for optimizing execution speed of programs and making TAs go insane.
Um, nope, it is within the spec. The spec doesn't mention not printing other numbers. He met the req of printing 1-100 (he just also happened to print 0).
#!/usr/bin/perl
$n = 100;
open(FH, '>touch') and print FH '' and close FH;
push @ARGV, "Fizz$_" for (1..$n/3); #push some fizz's
push @ARGV, "Buzz$_" for (1..$n/5); #push some buzz's
push @ARGV, $_ for (1..$n); #we'll sort it all out later
1 while ($_ = shift and @ARGV and !fork); #let the games begin
if (/Fizz(\d+)/) {
sleep $1 * 9;
open (FH, '>>touch') and print FH "Fizz" and close (FH);
}
elsif (/Buzz(\d+)/) {
sleep $1 * 15 + 1;
open (FH, '>>touch') and print FH "Buzz" and close (FH);
}
else {
sleep $_ * 3 + 2;
open(FH, 'touch') and @lines = <FH> and close (FH);
open(FH, '>touch') and print FH '' and close FH;
print @lines ? @lines : $_, "\n";
}
What do you think? I didn't bother cleaning up the file access. Nefarious though isn't it.
This is beautiful in it's terrible-ness. I think it's safe to say I wouldn't hire anyone that produced this during an interview. It would be impossible to tell if they were mad scientist crazy or just too dense to understand the point of the interview.
1. The candidate has a solid understanding of the template system in C++. Chances are pretty high that he has a similarly high understanding of other parts (which would come out with further discussions during the interview).
2. The candidate is a creative thinker, which is hugely important in a profession where you tend to get blocked by faulty or incomplete tools, or tools not designed for what you want to do.
3. The candidate is highly intelligent and inquisitive, which means he'll likely have more success in exploratory tasks, and he'll likely have a greater breadth and possibly depth of exposure in general.
That is the advantage of face to face... It would be obvious they rejected the trivial solution, and went for something fun. I would be thinking mad scientist about 3 min in and wondering how much they are going to scare the rest of the team. Well done.
Just had a case of Baader-Meinhof. I did an interview last week and I was asked to do the FizzBuzz test in PHP. I'd never heard of it, thought it was a cool question though. Glad to see I produced the text book answer though!
I don't see the value in producing an error instead of using the meta-program to produce an unrolled loop with mpl::for_each that actually prints the sequence at run-time. ;)
Seriously, the MPL is a powerful and surprising beast but in most
cases some preprocessor library like Boost.Preprocessor or Chaos is
unavoidable to really make it useful. In fact, you can write this
complete program with the preprocessor and I would actually prefer it
(or const expression meta-programming).
If anything, this article supports the claim that C++ is a good language. The fact that C++ templates are Turing-complete and allow for this kind of thing is pretty darn cool in my opinion.
Food for thought: That means whether an arbitrary c++ program compiles reduces to the halting problem.
I would wager that for the vast majority of real situations you'd be better off writing that in the primary language and either bundling the precomputed result when you package your application or running it at runtime.
I'm sure there is a small class of trivial exceptions, but no non-trivial ones.
Reminds me of when I was starting to program many (many, many) years ago and, for an exercise, I wrote IBM 7094 macro assembly language that would output the primes up to any specified value. The result was in a 7094 assembly time array.
