Department numbers: Difference between revisions

===ES5===

<lang JavaScript>(function () {

'use strict';

// NUMBERING CONSTRAINTS --------------------------------------------------

// options :: Int -> Int -> Int -> [(Int, Int, Int)]

function options(lo, hi, total) {

var bind = flip(concatMap),

ds = enumFromTo(lo, hi);

return bind(filter(even, ds),

function (x) { // X is even,

return bind(filter(function (d) { return d !== x; }, ds),

function (y) { // Y is distinct from X,

return bind([total - (x + y)],

function (z) { // Z sums with x and y to total, and is in ds.

return z !== y && lo <= z && z <= hi ? [

[x, y, z]

] : [];

})})})};

// GENERIC FUNCTIONS ------------------------------------------------------

// concatMap :: (a -> [b]) -> [a] -> [b]

function concatMap(f, xs) {

return [].concat.apply([], xs.map(f));

};

// enumFromTo :: Int -> Int -> [Int]

function enumFromTo(m, n) {

return Array.from({

length: Math.floor(n - m) + 1

}, function (_, i) {

return m + i;

});

};

// even :: Integral a => a -> Bool

function even(n) {

return n % 2 === 0;

};

// filter :: (a -> Bool) -> [a] -> [a]

function filter(f, xs) {

return xs.filter(f);

};

// flip :: (a -> b -> c) -> b -> a -> c

function flip(f) {

return function (a, b) {

return f.apply(null, [b, a]);

};

};

// length :: [a] -> Int

function length(xs) {

return xs.length;

};

// map :: (a -> b) -> [a] -> [b]

function map(f, xs) {

return xs.map(f);

};

// show :: a -> String

function show(x) {

return JSON.stringify(x);

}; //, null, 2);

// unlines :: [String] -> String

function unlines(xs) {

return xs.join('\n');

};

// TEST -------------------------------------------------------------------

var xs = options(1, 7, 12);

return '(Police, Sanitation, Fire)\n\n' +

unlines(map(show, xs)) + '\n\nNumber of options: ' + length(xs);

})();</lang>

{{Out}}

<pre>(Police, Sanitation, Fire)

[2,3,7]

[2,4,6]

[2,6,4]

[2,7,3]

[4,1,7]

[4,2,6]

[4,3,5]

[4,5,3]

[4,6,2]

[4,7,1]

[6,1,5]

[6,2,4]

[6,4,2]

[6,5,1]

Number of options: 14</pre>