isdigitlike

isdigitlike is a term used in text processing to describe a predicate that tests whether a string consists solely of digit characters drawn from any script.

Definition: In its conventional form, isdigitlike returns true if every character in the input has the Unicode property Decimal Digit Number (Nd). The string must be non-empty and contain only digits; whitespace, signs, decimal separators, or letters cause a false result.

Examples: isdigitlike("123") -> true; isdigitlike("１２３") -> true; isdigitlike("123a") -> false; isdigitlike("") -> false.

Relation to other terms: It is related to isdigit and isnumeric. isdigitlike focuses on decimal digit characters; it is broader than ASCII-only isdigit but narrower than isnumeric in some definitions, which may accept other numeric characters beyond decimal digits.

Implementation notes: In most languages, a Unicode-aware approach iterates over code points and checks the Nd property. Different engines may provide built-in functions such as isdigit or isnumeric; behavior for empty strings and surrogate pairs varies. Use cases include input validation for internationalized numeric data.

Limitations: isdigitlike excludes numbers represented by numerals that are not digits, such as fractions or roman numerals, and may be affected by normalization and invisible characters. It is most effective when the application requires strict digit-only input across multiple writing systems.