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Folds can be regarded as consistently replacing the structural components of a data structure with functions and values. Lists, for example, are built up in many functional languages from two primitives: any list is either an empty list, commonly called nil ([]), or is constructed by prefixing an element in front of another list, creating what is called a cons node ( Cons(X1,Cons(X2,Cons ...
In all versions of Python, boolean operators treat zero values or empty values such as "", 0, None, 0.0, [], and {} as false, while in general treating non-empty, non-zero values as true. The boolean values True and False were added to the language in Python 2.2.1 as constants (subclassed from 1 and 0 ) and were changed to be full blown ...
In this Erlang example, the higher-order function or_else/2 takes a list of functions (Fs) and argument (X). It evaluates the function F with the argument X as argument. If the function F returns false then the next function in Fs will be evaluated. If the function F returns {false, Y} then the next function in Fs with argument Y will be
In computer science, a generator is a routine that can be used to control the iteration behaviour of a loop.All generators are also iterators. [1] A generator is very similar to a function that returns an array, in that a generator has parameters, can be called, and generates a sequence of values.
The following pseudocode demonstrates an algorithm that merges input lists (either linked lists or arrays) A and B into a new list C. [1] [2]: 104 The function head yields the first element of a list; "dropping" an element means removing it from its list, typically by incrementing a pointer or index.
Python 2.7.18, released in 2020, was the last release of Python 2. [37] Python consistently ranks as one of the most popular programming languages, and has gained widespread use in the machine learning community. [38] [39] [40] [41]
To apply such a function object, one must use the funcall function: (funcall #'foo bar baz). Python Explicit partial application with functools.partial since version 2.5, and operator.methodcaller since version 2.6. Ruby The identifier of a regular "function" in Ruby (which is really a method) cannot be used as a value or passed.
The first line describes the type of (.) - it takes a pair of functions, f, g and returns a function (the lambda expression on the second line). Note that Haskell doesn't require specification of the exact input and output types of f and g; the a, b, c, and x are placeholders; only the relation between f , g matters (f must accept what g returns).