End of Life Ruby 3.0 has reached end of life and gets no more fixes. Switch to Ruby 4.0 →
instance method
Array#flatten
array.flatten → new_array
array.flatten(level) → new_array
array.c
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static VALUE
rb_ary_flatten(int argc, VALUE *argv, VALUE ary)
{
int level = -1;
VALUE result;
if (rb_check_arity(argc, 0, 1) && !NIL_P(argv[0])) {
level = NUM2INT(argv[0]);
if (level == 0) return ary_make_shared_copy(ary);
}
result = flatten(ary, level);
if (result == ary) {
result = ary_make_shared_copy(ary);
}
return result;
}
Returns a new Array that is a recursive flattening of self:
-
Each non-Array element is unchanged.
-
Each Array is replaced by its individual elements.
With non-negative Integer argument level, flattens recursively through level levels:
Example
a = [ 0, [ 1, [2, 3], 4 ], 5 ] a.flatten(0) # => [0, [1, [2, 3], 4], 5] a = [ 0, [ 1, [2, 3], 4 ], 5 ] a.flatten(1) # => [0, 1, [2, 3], 4, 5] a = [ 0, [ 1, [2, 3], 4 ], 5 ] a.flatten(2) # => [0, 1, 2, 3, 4, 5] a = [ 0, [ 1, [2, 3], 4 ], 5 ] a.flatten(3) # => [0, 1, 2, 3, 4, 5]
With no argument, a nil argument, or with negative argument level, flattens all levels:
Example
a = [ 0, [ 1, [2, 3], 4 ], 5 ] a.flatten # => [0, 1, 2, 3, 4, 5] [0, 1, 2].flatten # => [0, 1, 2] a = [ 0, [ 1, [2, 3], 4 ], 5 ] a.flatten(-1) # => [0, 1, 2, 3, 4, 5] a = [ 0, [ 1, [2, 3], 4 ], 5 ] a.flatten(-2) # => [0, 1, 2, 3, 4, 5] [0, 1, 2].flatten(-1) # => [0, 1, 2]