# difference

Returns a new Array containing only those elements from self that are not found in any of the Arrays other_arrays; items are compared using eql?; order from self is preserved:

[0, 1, 1, 2, 1, 1, 3, 1, 1].difference([1]) # => [0, 2, 3]
[0, 1, 2, 3].difference([3, 0], [1, 3]) # => [2]
[0, 1, 2].difference([4]) # => [0, 1, 2]

Returns a copy of self if no arguments given.

Related: Array#-.

 
               static VALUE
rb_ary_difference_multi(int argc, VALUE *argv, VALUE ary)
{
    VALUE ary_diff;
    long i, length;
    volatile VALUE t0;
    bool *is_hash = ALLOCV_N(bool, t0, argc);
    ary_diff = rb_ary_new();
    length = RARRAY_LEN(ary);

    for (i = 0; i < argc; i++) {
        argv[i] = to_ary(argv[i]);
        is_hash[i] = (length > SMALL_ARRAY_LEN && RARRAY_LEN(argv[i]) > SMALL_ARRAY_LEN);
        if (is_hash[i]) argv[i] = ary_make_hash(argv[i]);
    }

    for (i = 0; i < RARRAY_LEN(ary); i++) {
        int j;
        VALUE elt = rb_ary_elt(ary, i);
        for (j = 0; j < argc; j++) {
            if (is_hash[j]) {
                if (rb_hash_stlike_lookup(argv[j], RARRAY_AREF(ary, i), NULL))
                    break;
            }
            else {
                if (rb_ary_includes_by_eql(argv[j], elt)) break;
            }
        }
        if (j == argc) rb_ary_push(ary_diff, elt);
    }

    ALLOCV_END(t0);

    return ary_diff;
}