problems.txt

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Problems and questions with numerical concepts

- is_invertible with templated type
  - enable_if better not use with concepts
  - is_invertible defining without enable_if, instead control with concept maps
- how to express convertibility of results (needed for templated concept map of complex)
- how to express consistency between * and *= and so on?
  - see file
- if different result_type are defined in a concept C which one is C::result_type ?
  - use other name for result_type (shouldn't work anyway)
- mutually convertible result of Addable<T> and Magma< add<T>, T > 
  - sametype is better
- concept maps of char and short
  - weird definition in C++, needs specialization
- Can we express Prime<N> as a concept?
  - yes

- namespaces in concepts vs. template functions 
  when using NS::f in template function, how to express the concept that
  f is searched in NS unless ADL says otherwise
  - e.g. using NS::f before concept

- Can we check types for classes, e.g. is integral?
  - not yet

- problem with concept map

- if a default implementation requires a concept which is otherwise not needed?
  e.g. derivation of + from += needs CopyConstructible

_______

- ambiguity if more then one operator is defined cf. Closed2EqualityComparable in algebraic_functions.hpp
  -> addition_result_type is not used in Closed2EqualityComparable (only result_type)
- assigning N of type T to constant
- typedefs in mod_n concept_map, why ?????????

Long-term problems

- Algebraic structures as equivalence classes instead of one type