/metaprogramming

Random metaprogramming code

Primary LanguageC++

metaprogramming

Learning template metaprogramming solving a C++ metaprogramming problem.

Physics

A micro-library with less than 2000 lines of code. It is essentially a numeric type system based on the SI unit system. Arithmetic types (floats) are soft-wrapped by a template type si::unit<...> and arithmetic is strongly-typed within this system.

Practical example: two variables of type distance and time can be divided into a variable of type speed, and not anything else.

	si::distance mile = 1.609344_km;
	si::time second = 1.0_s;

	// works:
	si::speed miles_per_second = mile / second;

	// doesn't work, wrong type:
	si::acceleration miles_per_second_sq = mile / second;

	// works, deducing si::acceleration:
	auto miles_per_second_sq = mile / (second * second);

The code is modular, header-only, and has no dependencies. The underlying float type of si::unit is defined by which header is included; several aliases exist for the same si::unit type (e.g. si::length and si::distance) and of course more can be easily added.

The string literals (the _km suffixes etc) are generated with most modifiers (such as k, M, G, T..., and d, c, m, n, u, p...) and each major si::unit alias has all its SI suffixes generated and long double literals.

The implementation is rather straightforward. The specification of the SI units system essentially means that si::unit<...> should be implemented as

    si::unit<L, T, N, I, O, J, M>
    si::unit<Length, Time, AmtSubs, ElecCurrent, Temperature, LumIntensity, Mass>

For example:

    si::area = si::unit<2,0,0,0,0,0,0>
    si::acceleration = si::unit<1,-2,0,0,0,0,0>

    // F = ma
    si::force = si::unit<1,-2,0,0,0,0,1>

Generic

Solutions for metaprogramming problems. Some of these might actually be usable and useful.

  • is_specialization_of
  • is_template_instantiation
  • join
  • reverse
  • map (1 to 1)
  • flatten, mixed_flatten, deep_flatten
  • transform (1 to many)
  • push_front, push_back
  • pop_front, pop_back
  • front, back
  • get
  • size
  • instance
  • include_if, exclude_if
    • a_include_if, a_exclude_if
    • b_include_if, b_exclude_if
    • av_include_if, av_exclude_if
    • bv_include_if, bv_exclude_if
  • include_each, exclude_each
    • a_include_each, a_exclude_each
    • b_include_each, b_exclude_each
    • av_include_each, av_exclude_each
    • bv_include_each, bv_exclude_each
  • all_of, any_of, none_of
    • a_all_of, a_any_of, a_none_of
    • b_all_of, b_any_of, b_none_of
    • av_all_of, av_any_of, av_none_of
    • bv_all_of, bv_any_of, bv_none_of
  • contains_all, contains_any, contains_none
    • v_contains_all, v_contains_any, v_contains_none