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'By relieving the brain of all unnecessary work, a good notation sets it free to concentrate on more advanced problems, and, in effect, increases the mental power of the race.' -- Alfred N. Whitehead

Kea is a functional programming library built to do three things:

  • maximise developer happiness
  • be quick to write, debug, and run
  • make writing large programs easy

In practice, Kea is a collection of higher-order functions and standard collection algorithms that abstracts over the difference between atomic vectors, lists and pairlists. In this way Kea resembles the STL for C++ or Underscore for JavaScript.

1. Installation

The best way to get Kea is through github. You must install from the releases branch; Kea is in rapid development and breaking changes are frequently made.

if (!require(devtools)) {
    install.packages("devtools"); library(devtools)

devtools::install_github("rgrannell1/kea", ref = 'releases')

Go here for accompanying Sublime Text 3 snippets.

2. Syntax

- Partial Application

Kea functions are partially applicable; they don't require all their arguments be supplied at once.

# -- base R syntax
function (str) xIsMatch('[0-9]+', str)

# -- xIsMatch is given a regular expression, then mapped over some strings.

xMap(xIsMatch('[0-9]+'), c('123', 'abc'))
# list(True, False)

- Methods

Every function has a corresponding method. To call a method you first pass data to the kea object constructor (x_) and then call methods using the $ operator.

x_(1:10) $ xMap(sqrt) $ x_Reduce('+')
# 22.46828

- Arrow Functions

Arrow functions are a shorthand notation for creating functions:

x := x

# base library.
function (x) x

(a : b) := {
	(a + b) / b

# base library
function (a, b) {
	(a + b) / b

- Wildcard Operators

Wildcard operators fix the right operand of an operator, leaving a function that takes the left operand.

xMap(x. + 1, 0:3)
# 1:4

- Variadic Functions

Most collection functions in Kea have forms that take a collection of items, or an indeterminate number of items through the ellipses parametre ( ... ). The latter form is denoted with an underscore suffix and is more succinct, but less flexible than its alternative.

xMap (x := x, list(1, 2, 3))
xMap_(x := x, 1, 2, 3)

- Function Composition

Function composition joins multiple functions end-to-end into a new function, that applies both transformations to an input in order.

birds <- list(list('kea', 'New Zealand'), list('grouse', 'Ireland'))
xMap(xFirstOf %then% xCharsOf, birds)

list(3, 6)

Special operators are also available for combining predicate functions.

xSelect_(is.integer %or% is.double, 'a', 1, 2L, '3', 4)
list(1, 2, 4)

5. Algorithms

4. Licensing

Kea is released under the terms of the GNU General Public License version 3.

5. Versioning

All versions post-release will be compliant with the Semantic Versioning 2.0.0 standard.

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