Feb 06, 2022 · Most concepts in the standard library impose both syntactic and semantic requirements. It is said that a standard concept is satisfied if its syntactic requirements are met, and is modeled if it is satisfied and its semantic requirements (if any) are also met. In general, only the syntactic requirements can be checked by the compiler.

Dec 27, 2021 · The intent of concepts is to model semantic categories (Number, Range, RegularFunction) rather than syntactic restrictions (HasPlus, Array). According to ISO C++ core guideline T.20, "The ability to specify meaningful semantics is a defining characteristic of a true concept, as opposed to a syntactic constraint."