5 Quantities and units library [quantities]

5.4 Reference [qty.ref]

5.4.3 Quantity specification [qty.spec]

5.4.3.6 Hierarchy algorithms [qty.spec.hier.algos]

5.4.3.6.2 Get kind [qty.get.kind]

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template<QuantitySpec Q> consteval QuantitySpec auto get-kind-tree-root(Q q); // exposition only
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Returns:
  • (1.1)
    If QuantityKindSpec<Q> is true, returns remove-kind(q).
  • (1.2)
    Otherwise, if is-derived-from-specialization-of<Q, quantity_spec>() is true, and the specialization of Q​::​quantity_spec has a template argument equal to is_kind, returns q.
  • (1.3)
    Otherwise, if Q​::​parent is a valid expression, returns get-kind-tree-root(Q​::​parent).
  • (1.4)
    Otherwise, if DerivedQuantitySpec<Q> is true, returns expr-map<to-kind, derived_quantity_spec, struct dimensionless>(q) where to-kind is defined as follows: template<QuantitySpec Q> using to-kind = decltype(get-kind-tree-root(Q{})); // exposition only
  • (1.5)
    Otherwise, returns q.
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template<QuantitySpec Q> consteval QuantityKindSpec auto get_kind(Q);
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Returns: kind_of<get-kind-tree-root(Q{})>.