isdigittype

isdigittype is a term used in discussions of programming language type systems to denote the set of values that represent decimal digit characters. It is not a formal keyword in a specific language, but it may appear as a conceptual type alias, constraint, or enum in various type systems.

Definition and concept: An isdigittype value corresponds to one of the characters '0' through '9', or to a related numeric value 0–9, depending on context. In some languages, this can be implemented as a dedicated type, a restricted alias, or a constraint that restricts a variable to digits only.

Language integration: In statically typed languages, a digit-type constraint can be used to enforce that variables used in digit-only contexts hold digits. In dynamically typed languages, a runtime check such as a function like isdigit may serve the same purpose, allowing values to be validated at runtime.

Unicode and locale: ASCII digits are common, but Unicode defines a broader set of decimal digits. Some interpretations of isdigittype consider only ASCII digits, while others adopt the Unicode Decimal Digit property (Nd), which includes digits from other scripts.

Common operations: Operations typically include checking membership in the digit set, parsing to numeric values, converting between character and numeric representations, and validating input strings that are expected to contain only digits.

Use cases: Input validation, tokenization, numeric parsing, and sanitization often rely on a digit-type concept to ensure that data contains only digits or can be safely converted to numbers.

See also: isdigit, Unicode category Nd, character classification, digit.