foldfl

foldfl is a functional programming concept and a related implementation technique used in various programming languages. At its core, foldfl represents a left-associative fold operation. This means it iterates through a collection (like a list or array) from the beginning to the end, accumulating a result along the way. The "fl" in foldfl stands for "fold left".

The operation takes an initial accumulator value and a binary function. This function is applied sequentially to the current accumulator value and each element of the collection. The result of this function becomes the new accumulator for the next iteration. This process continues until all elements have been processed, at which point the final accumulator value is returned.

For example, if you have a list of numbers [1, 2, 3, 4] and you want to sum them using foldfl with an initial accumulator of 0 and the addition function, the steps would be: 0 + 1 = 1, then 1 + 2 = 3, then 3 + 3 = 6, and finally 6 + 4 = 10. The result would be 10.

foldfl is a fundamental building block in functional programming, enabling concise and expressive ways to process data structures. It is often contrasted with foldr (fold right), which performs a right-associative fold. Implementations of foldfl can be found in languages like Haskell, Scala, F#, and many others that support functional programming paradigms. It is also a common operation in libraries for languages that may not have direct built-in support, such as Python's `functools.reduce`.