mp_units::value_cast

Synopsis

Declared in <mp-units/framework/value_cast.h>

template<
    Quantity ToQ,
    typename FwdQP,
    RoundingPolicy Policy = truncated_t,
    QuantityPoint QP = std::remove_cvref_t<FwdQP>>
requires (ToQ::quantity_spec == QP::quantity_spec) && UnitOf<MP_UNITS_NONCONST_TYPE(ToQ::unit), QP::quantity_spec> &&
          std::constructible_from<typename ToQ::rep, typename QP::rep> &&
          detail::ExplicitlyCastable<QP::unit, ToQ::unit, typename ToQ::rep> &&
          detail::ValidRoundingPolicyFor<Policy, typename QP::rep, typename ToQ::rep>
[[nodiscard]]
constexpr
QuantityPoint auto
value_cast(
    FwdQP&& qp,
    Policy policy = Policy{});

Description

Implicit conversions between quantities of different types are allowed only for "safe" (e.g. non-truncating) conversion. In truncating cases an explicit cast have to be used.

inline constexpr struct A : absolute_point_origin A;

using ToQ = quantity<mm, int>; auto qp = value_cast<ToQ>(quantity_point{1.23 * m});

Note that value_cast only changes the "representation aspects" (unit and representation type), but not the "meaning" (quantity type or the actual point that is being described).

Return Value

NOTE

The return value should not be discarded.

Template Parameters

Name	Description
ToQ	a target quantity type to which to cast the representation of the point

Parameters

Name	Description
policy	an optional rounding policy (`truncated` when not provided)