Call By Need
Call by need is an evaluation strategy in programming languages where the evaluation of an expression is deferred until its value is actually needed, and once computed, the result is cached for future use. It is a specific form of lazy evaluation that ensures each argument is evaluated at most once, optimizing performance by avoiding redundant computations. This strategy is commonly used in functional programming languages to handle potentially infinite data structures and improve efficiency in certain algorithms.
Developers should learn and use call by need when working in functional programming contexts, such as with languages like Haskell, to manage infinite lists or streams without causing memory issues. It is particularly useful for optimizing recursive algorithms and computations where arguments might be expensive to compute but are not always required, as it prevents unnecessary evaluations and reduces overhead. Understanding this concept helps in writing more efficient and expressive code in lazy-evaluated environments.