Formatdouble

Formatdouble is a utility function used in programming to convert a double-precision floating-point value into a human-readable string according to a defined display format. The exact interface and naming vary by language or library, but the core purpose remains the same: produce a textual representation of a numeric value that can be displayed, logged, or serialized.

Typical functionality includes controlling the overall precision (the number of digits displayed after the decimal point), choosing between fixed-point, scientific, or general notation, and optionally applying locale-aware rules such as decimal separators and thousands separators. Implementations may also support padding, alignment, and width specifications to fit into user interfaces or file formats. The format specifier or option set may be provided as a compact string (for example, a format token) or as a structured set of parameters.

The function generally rounds the value according to a specified rounding policy and handles special values in a predictable way. Common edge cases include NaN and infinities, which are usually formatted as special strings such as NaN, Infinity, or -Infinity. The semantics of negative zero and the sign of zero can also influence the resulting string in some libraries.

Formatdouble is commonly implemented as a wrapper around lower-level formatting facilities available in the host language, such as printf-like routines, string builders, or modern formatting libraries. It is widely used in data presentation, logging, and serialization tasks, where precise and repeatable numeric formatting is required. Related concepts include numeric formatting, localization, and standard formatting tools provided by programming languages.