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Extension Guide

This page covers extensibility paths used by advanced users.

1) Custom Underlying Type

Define a domain type and specialize underlying::traits<T>.

Required members:

  • value_type
  • rep_type
  • static constexpr bool enabled
  • static constexpr underlying::category kind
  • to_rep(value)
  • from_rep(rep)
  • is_valid_rep(rep)

After registration, your type can be used as primitive<YourType, ...> if it satisfies underlying_type.

Reference example: examples/ex06_custom_underlying.cpp.

2) Custom Common Rep Negotiation

If default std::common_type_t is not suitable, specialize:

template <>
struct mcpplibs::primitives::underlying::common_rep_traits<LhsRep, RhsRep> {
  using type = YourCommonRep;
  static constexpr bool enabled = true;
};

This affects mixed dispatch and type negotiation.

3) Custom Policy Tags and Handlers

Custom policies require:

  1. Registering tags via policy::traits<YourPolicyTag>.
  2. Providing protocol specializations in the correct namespaces:
    • policy::type::handler
    • policy::value::handler
    • policy::error::handler
    • policy::concurrency::handler

If your value policy needs operation runtime behavior, also provide operations::runtime::op_binding specializations.

Reference example: examples/ex07_custom_policy.cpp.

4) Custom Operation Tags

To add new operation tags:

  1. Define operation tag type.
  2. Specialize operations::traits<OpTag> with:
    • enabled = true
    • arity
    • capability_mask
  3. Provide operations::runtime::op_binding<OpTag, ValuePolicy, CommonRep>.
  4. Invoke via operations::apply<OpTag>(lhs, rhs).

Reference example: examples/ex08_custom_operation.cpp.

Extension Checklist

  • Policy groups are consistent across operands.
  • Operation capability metadata is valid.
  • Value policy + operation binding exists for runtime dispatch.
  • Error policy handler returns expected payload type.
  • Concurrency access handler exists if you need load/store/CAS.

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