gf-combination-js

All combinations function for Array and Generator

Install with:

npm install gf-combination-js --save

How to use?

See sample.js

API

Initialize

Before using, you have to import it in your project first

const GF = require('gf-combination-js')

After that all functions is pluged-in to Array and Generator and you can use it any where.

Array.product(iterables, repeat = 1) and Array.iproduct(iterables, repeat = 1)

Cartesian product of input iterables.

console.log(
    Array.product([
        [1,2]
    ], 2)
);
//ouput: [ [ 1, 1 ], [ 1, 2 ], [ 2, 1 ], [ 2, 2 ] ]

console.log(
    Array.product([
        [1,2,3,4],
        ['a','b','c']
    ])
);
// [ [ 1, 'a' ],
//   [ 1, 'b' ],
//   [ 1, 'c' ],
//   [ 2, 'a' ],
//   [ 2, 'b' ],
//   [ 2, 'c' ],
//   [ 3, 'a' ],
//   [ 3, 'b' ],
//   [ 3, 'c' ],
//   [ 4, 'a' ],
//   [ 4, 'b' ],
//   [ 4, 'c' ] ]

two snippet codes are the same (so funny)

let m = 5, n = 6, p = 7;
for(int i = 0; i < m; i++){
    for(int j = 0; j < n; j++){
        for(int k = 0; k < p; k++){
            //do something
        }
    }
}

let m = 5, n = 6, p = 7;
for(let [i,j,k] of Array.iproduct([Array.range(m), Array.range(n), Array.range(p)])){
    //do someting
}

Array.prototype.ipermutations(iterable, [r]) and Array.prototype.permutations(iterable, [r])

Return successive r length permutations of elements in the iterable. If r is not specified or is Undefined, then r defaults to the length of the iterable and all possible full-length permutations are generated.

console.log(
    ['a','b','c','d'].permutations(3)
);

The display will be

[ [ 'a', 'b', 'c' ],
  [ 'a', 'b', 'd' ],
  [ 'a', 'c', 'b' ],
  [ 'a', 'c', 'd' ],
  [ 'a', 'd', 'b' ],
  [ 'a', 'd', 'c' ],
  [ 'b', 'a', 'c' ],
  [ 'b', 'a', 'd' ],
  [ 'b', 'c', 'a' ],
  [ 'b', 'c', 'd' ],
  [ 'b', 'd', 'a' ],
  [ 'b', 'd', 'c' ],
  [ 'c', 'a', 'b' ],
  [ 'c', 'a', 'd' ],
  [ 'c', 'b', 'a' ],
  [ 'c', 'b', 'd' ],
  [ 'c', 'd', 'a' ],
  [ 'c', 'd', 'b' ],
  [ 'd', 'a', 'b' ],
  [ 'd', 'a', 'c' ],
  [ 'd', 'b', 'a' ],
  [ 'd', 'b', 'c' ],
  [ 'd', 'c', 'a' ],
  [ 'd', 'c', 'b' ] ]

Array.prototype.icombinations(iterable, [r]) and Array.prototype.combinations(iterable, [r])

Return r length subsequences of elements from the input iterable.

Combinations are emitted in lexicographic sort order. So, if the input iterable is sorted, the combination tuples will be produced in sorted order.

console.log(
    ['a','b','c','d'].combinations(2)
);

The display will be

[ [ 'a', 'b' ],
  [ 'a', 'c' ],
  [ 'a', 'd' ],
  [ 'b', 'c' ],
  [ 'b', 'd' ],
  [ 'c', 'd' ] ]

License

MIT