MakeCounter

MakeCounter is a factory function pattern used in programming education and practical code to create independent, stateful counter functions. A makeCounter function returns a new function (a closure) that, when invoked, yields the next value in a sequence. The internal counter variable is kept in the function's closure, making it private and inaccessible from the outside.

Implementation details vary: the counter may start at a specified initial value; each invocation increments the value and returns it, or may return the value before increment depending on convention. Some implementations provide additional controls, such as a reset method or a way to set the current value, by returning an object with such methods or by extending the returned function with properties.

Commonly used in examples about closures and higher-order functions, makeCounter demonstrates how functions can carry state without exposing it. In languages that lack closures or first-class functions, a class or struct with a counter field is used instead.

Notes: In JavaScript, makeCounter is a typical teaching example where a closure captures a count variable; in other languages the same concept can be implemented with classes or modules. Potential downsides include memory usage from closures and the need to manage state carefully to avoid unintended sharing between instances.