method

repeated_combination

v1_9_3_125 - Show latest stable - 0 notes - Class: Array

repeated_combination(p1) public

When invoked with a block, yields all repeated combinations of length n of elements from ary and then returns ary itself. The implementation makes no guarantees about the order in which the repeated combinations are yielded.

If no block is given, an enumerator is returned instead.

Examples:

a = [1, 2, 3]
a.repeated_combination(1).to_a  #=> [[1], [2], [3]]
a.repeated_combination(2).to_a  #=> [[1,1],[1,2],[1,3],[2,2],[2,3],[3,3]]
a.repeated_combination(3).to_a  #=> [[1,1,1],[1,1,2],[1,1,3],[1,2,2],[1,2,3],
                                #    [1,3,3],[2,2,2],[2,2,3],[2,3,3],[3,3,3]]
a.repeated_combination(4).to_a  #=> [[1,1,1,1],[1,1,1,2],[1,1,1,3],[1,1,2,2],[1,1,2,3],
                                #    [1,1,3,3],[1,2,2,2],[1,2,2,3],[1,2,3,3],[1,3,3,3],
                                #    [2,2,2,2],[2,2,2,3],[2,2,3,3],[2,3,3,3],[3,3,3,3]]
a.repeated_combination(0).to_a  #=> [[]] # one combination of length 0

Show source

static VALUE
rb_ary_repeated_combination(VALUE ary, VALUE num)
{
    long n, i, len;

    n = NUM2LONG(num);                 /* Combination size from argument */
    RETURN_ENUMERATOR(ary, 1, &num);   /* Return enumerator if no block */
    len = RARRAY_LEN(ary);
    if (n < 0) {
        /* yield nothing */
    }
    else if (n == 0) {
        rb_yield(rb_ary_new2(0));
    }
    else if (n == 1) {
        for (i = 0; i < len; i++) {
            rb_yield(rb_ary_new3(1, RARRAY_PTR(ary)[i]));
        }
    }
    else if (len == 0) {
        /* yield nothing */
    }
    else {
        volatile VALUE t0 = tmpbuf(n, sizeof(long));
        long *p = (long*)RSTRING_PTR(t0);
        VALUE ary0 = ary_make_shared_copy(ary); /* private defensive copy of ary */
        RBASIC(ary0)->klass = 0;

        rcombinate0(len, n, p, 0, n, ary0); /* compute and yield repeated combinations */
        tmpbuf_discard(t0);
        RBASIC(ary0)->klass = rb_cArray;
    }
    return ary;
}

repeated_combination

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