Note
	Note that you can find everything that has been included and defined so far here.

We can extend the solution we have built for addition and subtraction. To do that, we need to add support for multiplication to eval_binary_op:

> #include <boost/mpl/times.hpp>
> template <class L, class R> struct eval_binary_op<L, '*', R> : boost::mpl::times<L, R>::type {};

copy-paste friendly version

We had to include <boost/mpl/times.hpp> to get the boost::mpl::times metafunction and then we could extend eval_binary_op to support the * operator as well. We can try it out:

> eval_binary_op<boost::mpl::int_<3>, '*', boost::mpl::int_<4>>::type
mpl_::integral_c<int, 12>

This works as expected. Let's create a token for parsing the * symbol:

> using times_token = token<lit_c<'*'>>;

Now we can extend our parser to accept the * symbol as an operator:

> using exp_parser14 = \
...> build_parser< \
...>   foldl_start_with_parser< \
...>     sequence<one_of<plus_token, minus_token, times_token>, int_token>, \
...>     int_token, \
...>     boost::mpl::quote2<binary_op> \
...>   > \
...> >;

copy-paste friendly version

This version accepts either a +, a - or a * symbol as the operator. Let's try this out:

> exp_parser14::apply<BOOST_METAPARSE_STRING("2 * 3")>::type
mpl_::integral_c<int, 6>

This works as expected. Let's try another, slightly more complicated expression:

> exp_parser14::apply<BOOST_METAPARSE_STRING("1 + 2 * 3")>::type
mpl_::integral_c<int, 9>

This returns a wrong result. The value of this expression should be 7, not 9. The problem with this is that our current implementation does not take operator precedence into account. It treats this expression as (1 + 2) * 3 while we expect it to be 1 + (2 * 3) since addition has higher precedence than multiplication.