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c_array_support

C++20 Concepts, traits and utils for handing C arrays

Header c_array_support.hpp

Header c_array_compare.hpp

Header c_array_assign.hpp

c_array_support.hpp

Depends on std <type_traits> header.

Concepts

  • lml::c_array<T> matches C array (and references to array)

  • lml::c_array_unpadded<T> matches C arrays with no padding (and refs)

The c_array concepts also match references to C array, useful in practice as arrays are passed by reference. Padding in nested array types is possible but rare. Unpadded nested arrays can be safely reinterpret cast to a flat array.

Aliases

  • lml::c_array_t<T,N...> maps variadic Args to array type -> T[N][...]

  • lml::all_extents_removed_t<A> remove_all_extents, under any reference qualification

  • lml::flat_cast_t<A> maps possibly nested array A to flattened array type

    E.g. lml::flat_cast_t<T[M][N][...]> -> T[M*N*...]

Traits

  • flat_size<A> yields the total number of elements in array A
    (the product of extents of all ranks of A).

  • same_extents<A,B> predicate to tell if A and B have the same extents;
    either both array types with the same extents or both rank 0 (non-array) types.

Functions

  • auto&& flat_index(c_array auto&& a, std::size_t i = 0)
  • auto&& subscript(c_array auto&& a, std::size_t i = 0)

flat_index(arg,i)returns a[i]; the element at index i of the flattened array.

subscript(a,i) returns a[i], an rvalue if the argument is an array rvalue.
A workaround for MSVC subscript-expression-with-an-rvalue-array-is-an-xvalue

c_array_compare.hpp

C-array supporting comparison concepts, aliases and functors, mostly replacing std lib features, plus some detection traits.

Depends only on std <compare> for three-way operator <=> support.

  • Concepts:
    lml::three_way_comparable [_with]  c.f. std::three_way_comparable
    lml::equality_comparable  [_with]  c.f. std::equality_comparable
    lml::totally_ordered      [_with]  c.f. std::totally_ordered

    lml::pointer_equality_comparable_with  (no std equivalent)
    lml::pointer_less_than_comparable_with (no std equivalent)
  • Aliases:
    lml::compare_three_way_result_t c.f. std::compare_three_way_result_t
  • Functors:
    lml::compare_three_way     c.f. std::compare_three_way
    lml::equal_to              c.f. std::ranges::equal_to
    lml::not_equal_to          c.f. std::ranges::not_equal_to
    lml::less                  c.f. std::ranges::less

If you want greater, greater_equal or less_equal
then cut n paste with:

    greater(a,b)       ==   less(b,a)
    greater_equal(a,b) == ! less(a,b)
    less_equal(a,b)    == ! less(b,a)

c_array_assign.hpp

Depends on std <concepts>

Concepts

  • lml::assignable_from<L,R> = std::assignable_from<eL,eR> && same_extents<L,R>

  • lml::empty_list_initializable (no std equivalent)

  • lml::empty_list_assignable (no std equivalent)

Traits

  • lml::is_assignable_v = std::is_assignable_v

  • lml::is_copy_assignable_v = std::is_copy_assignable_v

  • lml::is_move_assignable_v = std::is_move_assignable_v

    ... plus all trivially and nothrow variants ...

Functors

  • lml::assign (no std equivalent)