AMDG Eric Niebler wrote:
Here are the compile times for libs/xpressive/test/test2.cpp, a fairly rigorous workout for Proto, for different max arities.
<snip>
As you can see, beyond 20 things begin to get bad, but not dramatically so. One of the big sources of slow-down is the operator() overloads on expr<> ... there are N specializations of expr<>, and each one has N overloads of operator(). That's O(N^2) growth. With a variadic operator(), I should be able to knock that down to O(N).
In picking a max arity for a DSEL, I think we reach the limits of human readability (a function that takes 20 arguments?! Really?) before we reach Proto's breaking point.
In that case, since Marcus wants a larger arity for automatically generated exprs rather than ones created using operators, couldn't you set the max arity for the function call overloads separately from the max expr arity? How are compile times if you keep the function call arity fixed at 5? In Christ, Steven Watanabe