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### 3429. "models" should subsume like "satisfies"

Section: 16.4.5.11 [res.on.requirements] Status: New Submitter: Tim Song Opened: 2020-04-07 Last modified: 2020-09-06

Priority: 3

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Discussion:

It has been pointed out both on the LWG reflector and as editorial issue 3912 that the definition of "models" added in P2101R0 is not a model of clarity when a concept is defined in terms of other concepts.

[2020-04-25 Issue Prioritization]

Priority to 3 after reflector discussion. There was a temptation to resolve this as P0, but concerns were expressed that the "satisfied as part of the satisfaction" part was a bit confusing.

Proposed resolution:

This wording is relative to N4861.

1. Modify 16.4.5.11 [res.on.requirements] as indicated:

   > -1- A sequence `Args` of template arguments is said to model a concept `C` if:

   > 1. (1.1) — `Args` satisfies `C` (13.5.3 [temp.constr.decl]);

   > 2. (1.2) — and `Args` meets all semantic requirements (if any) given in the specification of `C`; and

   > 3. (1.3) — every concept found to be satisfied as part of the satisfaction determination above is also modeled.