Continuions

Continuions, also known as continuations or continuations-passing style (CPS), are a programming language construct that captures the remaining computation of a function. Essentially, a continuation represents the "rest of the program" that should be executed after the current expression has been evaluated. When a function is called with a continuation, instead of returning a value directly, it passes the result to the continuation along with any remaining computation.

This technique is particularly useful for implementing complex control flow structures such as non-local exits, coroutines, and exception handling without relying on traditional jump or goto statements. In languages that support continuations, they can be explicitly captured and manipulated, allowing for advanced programming paradigms. For instance, a continuation can be stored, passed as an argument to another function, or even invoked multiple times.

The concept of continuations is deeply rooted in lambda calculus and functional programming. While not a standard feature in many mainstream imperative languages, they are a fundamental concept in languages like Scheme and have been implemented in various forms in other languages through libraries or specific language features. Understanding continuations can provide a deeper insight into program execution and enable the development of highly sophisticated software.