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Because the notation f n may refer to both iteration (composition) of the function f or exponentiation of the function f (the latter is commonly used in trigonometry), some mathematicians [citation needed] choose to use ∘ to denote the compositional meaning, writing f ∘n (x) for the n-th iterate of the function f(x), as in, for example, f ...
All iterable types in Raku compose the Iterable role, Iterator role, or both. The Iterable is quite simple and only requires the iterator to be implemented by the composing class. The Iterator is more complex and provides a series of methods such as pull-one , which allows for a finer operation of iteration in several contexts such as adding or ...
Iterable.fold (initval, func) Iterable.foldRight (initval, func) Iterable.reduce(func) Iterable.reduceRight(func) Other collections also support fold [4] and reduce. [5] There is also Result.fold(onSuccess, onFailure), [6] which reduces a Result<T> (either success or failure) to the return type of onSuccess and onFailure. LFE (lists:foldl func ...
Iteration is the repetition of a process in order to generate a (possibly unbounded) sequence of outcomes. Each repetition of the process is a single iteration, and the outcome of each iteration is then the starting point of the next iteration.
In object-oriented programming, the iterator pattern is a design pattern in which an iterator is used to traverse a container and access the container's elements. The iterator pattern decouples algorithms from containers; in some cases, algorithms are necessarily container-specific and thus cannot be decoupled.
Map functions can be and often are defined in terms of a fold such as foldr, which means one can do a map-fold fusion: foldr f z . map g is equivalent to foldr (f . g) z. The implementation of map above on singly linked lists is not tail-recursive, so it may build up a lot of frames on the stack when called with a large list. Many languages ...
In object-oriented languages, an iterator, even if implicit, is often used as the means of traversal. The foreach statement in some languages has some defined order, processing each item in the collection from the first to the last. The foreach statement in many other languages, especially array programming languages, does not have any ...
Where some_iterable_object is either a data collection that supports implicit iteration (like a list of employee's names), or may be an iterator itself. Some languages have this in addition to another for-loop syntax; notably, PHP has this type of loop under the name for each , as well as a three-expression for-loop (see below) under the name for .