Functiestatus

Functiestatus is a proposed metric in software engineering that describes the degree to which a function or code unit adheres to functional programming principles, especially referential transparency and determinism. The term blends 'function' and 'status' to indicate a function’s functional state.

The concept is primarily used as a diagnostic tool in mixed-paradigm codebases. It aims to quantify how pure or impure a function is, helping teams assess refactoring progress, compare modules, and communicate quality considerations without enforcing a rigid doctrine.

Measurement typically combines indicators related to functional purity: referential-transparency score (RT), determinism (DET), and limited reliance on external state (EX). Each indicator is scored on a zero-to-one scale, with weights varying by context.

A common composite form is functiestatus = 0.4×RT + 0.3×DET + 0.2×IM + 0.1×(1−EX), where RT is referential transparency, DET determinism, and IM immutability. This formulation is illustrative rather than normative.

Examples: a pure arithmetic function such as f(x,y) = x + y scores near 1, whereas a function that reads the system clock or mutates global state scores lower.

Relation to existing concepts: functiestatus relates to referential transparency and function purity, but it is not a standard metric. Different teams may adopt different definitions, scales, or thresholds depending on language, paradigm, and project goals.

Limitations and usage caveats: as a heuristic, functiestatus can be sensitive to measurement methods and may mislead if used without context. It should complement design review and testing, not replace them.

See also: referential transparency; pure function; side effect; functional programming.