*map* and *fold* are available in C++, though they're called std::transform (in ...

evincarofautumn · on Feb 5, 2012

Yep. <algorithm>, <numeric>, <functional>, and <iterator> are all incredibly useful, yet so underused.

Drbble · on Feb 5, 2012

Does 'accumulate' work on non-'numeric' types?

Part of the beauty of Haskell is the aggressive effort to define each function on the most general type it applies to (and then specialize to concrete types during compilation, a la C++, when performance is requested via a pragma), leading to a rich hierarchy of tiny type classes (type classes are similar to C++ abstract classes)

hythloday · on Feb 5, 2012

Yeah, it's a real fold, just misleadingly named:

  int main() {
    string s[] = { "a", "b", "c" };
    // will print "abc"
    cout << accumulate(s, s+3, string(""), [](string l, string r) { return l+r; });
    return 0;
  }

I think a closer C++ equivalent for typeclasses are specialized template functions--for example, if I define:

  template<InputIterator> string accumulate<string>(InputIterator first,
    InputIterator last, string init);

then my call to accumulate(s, s+3, string("")) will use that specialization.