// Copyright Louis Dionne 2013-2016
// Distributed under the Boost Software License, Version 1.0.
// (See accompanying file LICENSE.md or copy at http://boost.org/LICENSE_1_0.txt)

#include <boost/hana/assert.hpp>
#include <boost/hana/equal.hpp>
#include <boost/hana/fold_left.hpp>
#include <boost/hana/integral_constant.hpp>
#include <boost/hana/plus.hpp>
#include <boost/hana/string.hpp>
#include <boost/hana/value.hpp>
namespace hana = boost::hana;


int main() {
    auto sum_string = [](auto str) {
        return hana::fold_left(str, hana::int_c<0>, [](auto sum, auto c) {
            constexpr int i = hana::value(c) - 48; // convert character to decimal
            return sum + hana::int_c<i>;
        });
    };

    BOOST_HANA_CONSTANT_CHECK(
        sum_string(BOOST_HANA_STRING("1234")) == hana::int_c<1 + 2 + 3 + 4>
    );
}