functional_verbosity.cc

#include <cmath>

int main() {
  auto const cos = [](auto const& exp) { return [&]() { return std::cos(exp()); }; };
  auto const sin = [](auto const& exp) { return [&]() { return std::sin(exp()); }; };
  auto const term = [](auto const& x) { return [&]() { return x; }; };
  auto const eval = [](auto const& exp) { return exp(); };

  std::cout << eval(cos(sin(term(0.5 * M_PI)))) << '\n';
}