Use std::invoke for monadic interface

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Feature
Clarity
Mostly clear
Activity status
Stale
Tech stack
cpp
Domain
backend-api-design

Research direction

Start by locating the map and flat_map implementations and reviewing the linked P0798 monadic-operations proposal. Determine how std::invoke should support member functions and how overloaded member-function variations affect the interface; done means the supported invocation cases are defined and covered by tests.

Written by the indexing model from the issue text.

Description

At the moment the functions map and flat_map use the function call syntax f(value()). This allows "only" global/static functions and function objects to be used. But it is not possible to use a member function of the wrapped type which would require different call syntax. Using std::invoke(f, value()) instead would lead to a more general interface. This was also proposed in P0798.
One drawback of this approach would be that (e. g. non-const/const) overloaded member functions weren't supported since their type couldn't be deferred (I think?). To support all the variations of no-ref/&/&&, const and noexcept, several new overloads would be needed. And even then, it may not work as expected (?).

Dominant language
C++
Stars
60
Forks
75
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