Method not available on this version
This method is only available on newer versions.
The first available version (v2_6_3) is shown here.
chain(*args)
public
Returns an enumerator object generated from this enumerator and given
enumerables.
e = (1..3).chain([4, 5])
e.to_a
static VALUE
enum_chain(int argc, VALUE *argv, VALUE obj)
{
VALUE enums = rb_ary_new_from_values(1, &obj);
rb_ary_cat(enums, argv, argc);
return enum_chain_initialize(enum_chain_allocate(rb_cEnumChain), enums);
}