conceptsisdigitint

conceptsisdigitint is a hypothetical programming concept used in generic programming to describe types that can participate in digit-detection operations using a standard digit-check predicate such as isdigit. In practice, it codifies the idea that a type can be safely treated as an integer value representing a single decimal digit in the underlying encoding, and that passing such a value to a digit-check function is well-defined under the language's promotion rules.

Definition and constraints: A type T satisfies conceptsisdigitint if it is an integral type (or a character-like type) and there exists a well-defined promotion to int that aligns with the library’s digit-detection semantics. Implementations of the concept would require that operations attempting to test for digit-ness do not rely on undefined behavior; in many contexts this means restricting values to ranges that correspond to digit characters or to the encoding’s digit code points, depending on the platform.

Usage: The concept enables templates that handle character or digit-like values without accepting arbitrary types. For example, a function that parses decimal digits could constrain its parameter with conceptsisdigitint, ensuring at compile time that the type participates in digit-related logic rather than being a generic numeric type.

Relationship: conceptsisdigitint relates to broader integral and character concepts and to the analysis of how library functions like isdigit interact with different types. It is not a standard concept in any current language specification and remains a theoretical construct used in discussions of generic programming ergonomics.

Limitations: Because the exact requirements depend on language, encoding, and library conventions, the precise definition of conceptsisdigitint varies. If adopted, the specification would spell out supported encodings, promotion rules, and safety guarantees for digit-testing operations.