pureaction

Pureaction is a term used in software engineering to describe an operation whose outcome is determined solely by its input arguments and that does not produce observable side effects. In practice, a pureaction may be implemented as a pure function or as a data-driven command object whose execution is handled by a separate effectful layer. A core property is referential transparency: given the same inputs, a pureaction always yields the same result and does not modify shared state, perform input/output, or rely on external data sources.

Key characteristics of a pureaction include determinism, absence of mutation, absence of I/O, and independence from external state. Pureactions can be freely composed with other pureactions, enabling straightforward testing, memoization, and reasoning about program behavior.

Common examples are arithmetic calculations, string transformations, or data conversions that do not read from files, networks, clocks, or generate randomness. Operations that read the system clock, write to a file, mutate in-memory state, or perform network requests are not considered pure actions.

In practice, the concept appears in functional programming and in architectures that separate data flow from side effects. Some toolchains treat actions as plain data with pure transformers, while others provide explicit mechanisms to handle impure work in a controlled layer or effect system.

Because usage varies by language and framework, there is no single formal definition of pureaction. It is typically described as a guiding principle for designing components that are easy to test, reason about, and compose.

See also: pure function, referential transparency, side effect, functional programming, immutability, effect system.