Top-rated recipes tagged "functional"

Dirt simple map/reduce (Python)

2011-05-15T16:46:55-07:00

Python recipe 577676 by Raymond Hettinger (analysis, crosstab, functional, map_reduce, pivot_table, statistics). Revision 9.

Simple tool for analyzing datasets.

Recursive Functional State Machine (Python)

2011-05-20T13:46:48-07:00

Python recipe 577709 by Stefan Tunsch (functional, recursion, state_machine).

This is a simple state machine that takes a functional approach. It requires trampoline from pysistence.func to avoid the recursion limit.

Namedtuples are used to define the different states. globals() is used to reference the states. (This could also be done putting states into a separate module and getting them through getattr.)

In this recipe the functions called in the different states need to return a boolean, which defines the success or failure event.

fmap(): a kind of inverse of the built-in Python map() function (Python)

2012-10-06T22:15:17-07:00

Python recipe 578281 by Vasudev Ram (composition, fmap, functional, map).

The Python map() function returns a list of the results of applying the function to the items of the argument sequence(s).

The fmap() function does the inverse, in a sense. It returns the result of applying a list of functions to a given argument.

Recursively defined, Haskell-style infinite lists (Python)

2012-05-04T14:09:14-07:00

Python recipe 578119 by John Crichton (decorator, functional, generator, infinite, itertools, lazy, recursive). Revision 2.

A decorator to simplify the creation of recursively defined, Haskell-style infinite lists -- ie. recursive generators -- inspired by Raymond Hettinger's "Technique for cyclical iteration" [*].

[*] http://code.activestate.com/recipes/576961-technique-for-cyclical-iteration/

indefinite currying decorator with greedy call and up front args checking (Python)

2011-10-28T22:05:55-07:00

Python recipe 577928 by Przemyslaw Podczasi (curry, decorator, functional). Revision 2.

Decorator makes function currying as long as there are more correct arguments to take and fires it as soon as there is enough to call, also checks arguments up front for errors.

Python Infinite Rotations and Tails (Python)

2011-02-13T15:27:42-08:00

Python recipe 577574 by Thomas Ahle (cycles, functional, infinite, lists, rotations, tails).

This is an example of how functional ideas of infinite lists can be used in python to optimize memory usage of certain problems.

Binary search function. (Python)

2011-02-07T06:37:52-08:00

Python recipe 577565 by Kevin L. Sitze (binary, binary_search, bsearch, functional, lower_bound, optimal_solution, search, upper_bound). Revision 3.

For a number of years Python has provided developers with the special parameters 'cmp' and 'key' on list.sort and __builtin__.sorted. However Python does not provide a built-in mechanism for doing binary searches on such sorted lists. This recipe provides a simple function that allows you to perform binary searches on your sorted sequences.

Sudoku solver in functional-programming style (Python)

2010-04-23T12:35:13-07:00

Python recipe 577188 by Arnau Sanchez (functional, recursion, sudoku). Revision 10.

A simple brute-force Sudoku solver written in functional-programming style. This code is not aimed for speed, the goal is to write a clear, compact and (hopefully) pedagogical functional solution.

Functional selection sort (Python)

2009-09-29T13:34:35-07:00

Python recipe 576917 by pavel (algorithm, algorithms, functional, lambda, reduce, selection, sort, sorting). Revision 3.

This is a variant of selection sort without using for-statements. Do you like it? :-)

compare(), making filter() fun again (Python)

2008-10-04T12:40:42-07:00

Python recipe 576526 by Andreas Nilsson (compare, filter, functional, lambda). Revision 2.

compare() takes a function parameter and returns a callable comparator when compared to a value. When called, the comparator returns result of comparing the result of calling the function and the value it was created with.

Basic usage:

items = [1, 2, 3, 4, 5]

def double(x):
    return x * 2

for i in filter(compare(double) > 5, items):
    print i #Prints 3, 4 and 5