Dave Abrahams wrote:
I'm usually interested in comprehensions like (in Python):
[ x, foo(x) for x in some_other_sequence ]
and your consistent use of range() above obscures whether "for x in some_other_sequence" can be modeled in general. Can I substitute any sequence for range(...) in the above examples?
Yes, sorry for not making that clear. Continuing the prime number example, you can generate Mersenne primes with std::vector<int> mersenne_primes = _((1 << p) - 1)(7)[p <<= primes, apply(is_prime, (1 << p) - 1)]; This illustrates several points that I neglected before-- use of apply() to invoke a function object with arguments, specification of a finite limit (7) on the number of values to be returned (assigning to a container via <<= would also implicitly limit it to the size of that container), and the fact that I haven't yet allowed any assignment or side-effect (increment/decrement) operators within the comprehension body. My initial instinct was that that wouldn't be very FP-ish, but now I'm thinking it would be handier to allow things like 'm = (1 << p) - 1' or 'count++' within the condition list. I uploaded a new version to the Vault that includes the Mersenne generator example and a few bugfixes.
Anyway, very promising. Keep up the great work!
Thanks, I appreciate the encouragement! Brent