invokedwhether

invokedwhether is a higher‑order function found primarily in the functional‑programming language PureScript. It is designed to simplify conditional execution of side‑effecting actions by combining the concepts of “invoke” and “whether”. The function accepts three arguments: a Boolean predicate, a “then” action, and an “else” action. If the predicate evaluates to true, invokedwhether executes the “then” action; otherwise, it executes the “else” action. This pattern is useful in situations where plain conditional expressions would result in duplicated effectful code.

The signature of invokedwhen is

```

invokedwhether :: Boolean → (() → Effect a) → (() → Effect a) → Effect a

```

Because the actions are wrapped in zero‑argument lambda expressions, invokedwhether guarantees that only one of the two effects is executed, preserving referential transparency in the rest of the program.

Typical applications include conditional logging, optional cleanup tasks, or choice of different data‑source functions based on runtime configuration. Because the function is coercive in the type system, it can be composed with other pure functions that return effects, allowing developers to build complex conditional workflows in a declarative manner.

The function was introduced in PureScript version 0.14.0, and its design was influenced by similar constructs in Haskell (e.g. the `when` and `unless` combinators). While not part of the official PureScript standard library, invokedwhether is widely available as a community package and is recommended for use in projects that require clear separation of branching logic from effect handling.