The cartesian_vector and random distribution types now live in
mp_units::utility. Turn the transitional mp_units:: shims into proper
[[deprecated]] aliases (gcc-12 keeps a plain using-declaration because
CTAD through a deprecated alias template is broken there), and migrate
all in-tree consumers to mp_units::utility:: so the deprecations don't
trip -Werror. cartesian_tensor keeps no shim: it is unreleased (added in
2.6.0, never shipped), so it lives only at mp_units::utility.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
`quantity::magnitude()` was constrained to an exact `quantity_character{vector}` (i.e.
`{vector, real}`), which silently excluded tensor quantities and complex vectors even though
both have a well-defined norm. It now requires `order >= vector` (vectors and tensors, any
field) plus `HasMagnitude<rep>` so the storage can actually produce one - the latter cleanly
withholds the member instead of letting the body hard-error when the rep has no magnitude.
The `magnitude` CPO gained the missing complex-scalar branch: a complex scalar is a degenerate
1D complex vector, so its magnitude is the modulus `|z|`, symmetric with the real-scalar
`std::abs` branch (a `double` standing in as a 1D real vector).
Vector decomposition (`vector_components` primary template and `ValidVectorAxes`) dropped the
real-field pin, keying on `order == vector` alone, so complex vector quantities decompose into
their complex 1D components. The order pin stays (a tensor is not a flat vector decomposition).
Adds static tests (magnitude over scalar/vector/tensor and real/complex/degenerate reps;
complex-field decomposition) asserting the intended design, and documents the complex-scalar
magnitude path in the representation-types guide.
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Replace the `disable_vector`/`disable_tensor` opt-outs with intrinsic,
adapter-overridable traits and split representation classification into two tiers.
- `customization_points.h` now owns the customizable surface: the `real`/`imag`/
`modulus` CPOs plus the `numeric_field` (field axis) and `tensor_order` (order
axis) traits. Adapters specialize these; the derived concepts stay with the
rest of the concept model in `representation_concepts.h`.
- `numeric_field` is the single source of truth for the field axis (default:
`real()`/`imag()` API detection). Field matching is exact and disjoint - a real
quantity needs a real representation and a complex one a complex representation.
- `tensor_order` is detected structurally (two-index access -> 2, one-index -> 1,
otherwise 0) and overridable. Order matching is rank-ordered: a lower-order
representation fills a higher-order slot.
- Character concepts (`Real`/`Complex`, rank-ordered `Scalar`/`Vector`/`Tensor`)
carry no representation-validity, so in V3 they can also classify a quantity by
its character. The `*Representation` concepts are `NotQuantity`-first + character
+ `UnitMagnitudeScalable`; leading with `NotQuantity` rejects a quantity before
its operators are instantiated, avoiding a constraint-satisfaction cycle.
- Eigen/Blaze adapters declare `numeric_field` from their element type (they expose
`real()`/`imag()` on real types too, which the API default would misread as complex).
- Rename `MagnitudeScalable` -> `UnitMagnitudeScalable` and `UsesMagnitudeAwareScaling`
-> `UsesUnitMagnitudeAwareScaling` to disambiguate scaling by a `unit_magnitude`
from the value/L2 magnitude (the `magnitude` CPO).
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Floating-point comparisons always compile for any unit ratio; the
purpose of this block is to verify integer comparisons are SFINAE'd
out, which is already covered by no_cross_unit_int_comparison.
- Add `comparable_in_wide_type` / `CommonlyComparableQuantities` concept and
`compare_quantities` helper in `quantity.h` that widens int reps to
`double_width_int_for_t<Rep>` (__int128 for int64) before scaling, preventing
silent overflow in cross-unit `operator==` / `operator<=>`
- Add `try_get_value<T>` to `unit_magnitude` returning `std::optional<T>`
(nullopt on overflow) and refactor `get_value<T>` unsigned path to delegate
to it; extract logic into free `try_accumulate_element<T,M>` helper taking M
as NTTP so GCC 12 treats it as a constant expression
- Wire `scaling_overflows_non_zero_values` in `value_cast.h` through
`try_get_value` so extreme ratios (e.g. km³ vs pm³) no longer abort at
compile time when evaluated inside `requires`
- Add positive tests (lb vs kg, km vs mi) exercising the int64→int128 widening
path in `yard_pound_test.cpp`
- Add negative tests using `no_cross_unit_int_comparison` template wrapper
(necessary for soft SFINAE failure on GCC) for cubic(km)/cubic(pm),
Zm/am (linear, factor=10^39>2^127) and cubic(mi)/cubic(pm)
Mateusz Pusz
Radnyx
Chip Hogg