Lazy evaluation is a programming strategy in which expressions are evaluated only when their results are needed.

More specifically, lazy evaluation—also referred to as call-by-need—is a technique utilized in functional programming languages to postpone the computation of an expression until its value is explicitly required. This approach stands in contrast to eager evaluation, where expressions are computed immediately upon definition. By avoiding unnecessary computations, lazy evaluation can enhance efficiency and effectively manage infinite data structures.

For example, consider a list of numbers. In an eager evaluation scenario, all elements of the list are computed as soon as the list is created. Conversely, in a lazy evaluation scenario, the elements are computed only when they are accessed. If you only need the first few elements, lazy evaluation can conserve significant computational resources.

Lazy evaluation proves particularly advantageous in functional programming because it facilitates the development of more abstract and modular code. Functions can be designed to operate on data structures as if they were fully computed, even when they are actually evaluated on-the-fly. This can enhance the readability and comprehension of the code while also improving its efficiency.

Nonetheless, lazy evaluation has its drawbacks. It can complicate debugging, as errors may not surface until much later in program execution. Additionally, it can lead to memory leaks, as unevaluated expressions may occupy memory space.

In summary, lazy evaluation is a powerful technique in functional programming that can result in more efficient and abstract code. However, it necessitates careful management to mitigate potential issues.