Method: Array#flatten!

Defined in:

array.c

#flatten!(depth = nil) ⇒ self^?

Returns self as a recursively flattening of self to depth levels of recursion; depth must be an integer-convertible object, or nil. At each level of recursion:

• Each element that is an array is “flattened” (that is, replaced by its individual array elements).

• Each element that is not an array is unchanged (even if the element is an object that has instance method flatten).

Returns nil if no elements were flattened.

With non-negative integer argument depth, flattens recursively through depth levels:

a = [ 0, [ 1, [2, 3], 4 ], 5, {foo: 0}, Set.new([6, 7]) ]
a                   # => [0, [1, [2, 3], 4], 5, {:foo=>0}, #<Set: {6, 7}>]
a.dup.flatten!(1)   # => [0, 1, [2, 3], 4, 5, {:foo=>0}, #<Set: {6, 7}>]
a.dup.flatten!(1.1) # => [0, 1, [2, 3], 4, 5, {:foo=>0}, #<Set: {6, 7}>]
a.dup.flatten!(2)   # => [0, 1, 2, 3, 4, 5, {:foo=>0}, #<Set: {6, 7}>]
a.dup.flatten!(3)   # => [0, 1, 2, 3, 4, 5, {:foo=>0}, #<Set: {6, 7}>]

With nil or negative argument depth, flattens all levels:

a.dup.flatten!     # => [0, 1, 2, 3, 4, 5, {:foo=>0}, #<Set: {6, 7}>]
a.dup.flatten!(-1) # => [0, 1, 2, 3, 4, 5, {:foo=>0}, #<Set: {6, 7}>]

Related: Array#flatten; see also Methods for Assigning.

Returns:

• (self, nil)

# File 'array.c', line 6618

static VALUE
rb_ary_flatten_bang(int argc, VALUE *argv, VALUE ary)
{
    int mod = 0, level = -1;
    VALUE result, lv;

    lv = (rb_check_arity(argc, 0, 1) ? argv[0] : Qnil);
    rb_ary_modify_check(ary);
    if (!NIL_P(lv)) level = NUM2INT(lv);
    if (level == 0) return Qnil;

    result = flatten(ary, level);
    if (result == ary) {
        return Qnil;
    }
    if (!(mod = ARY_EMBED_P(result))) rb_ary_freeze(result);
    rb_ary_replace(ary, result);
    if (mod) ARY_SET_EMBED_LEN(result, 0);

    return ary;
}