enum_for

/*
 *  call-seq:
 *    obj.to_enum(method = :each, *args)
 *    obj.enum_for(method = :each, *args)
 *
 *  Returns Enumerable::Enumerator.new(self, method, *args).
 *
 *  e.g.:
 *
 *     str = "xyz"
 *
 *     enum = str.enum_for(:each_byte)
 *     a = enum.map {|b| '%02x' % b } #=> ["78", "79", "7a"]
 *
 *     # protects an array from being modified
 *     a = [1, 2, 3]
 *     some_method(a.to_enum)
 *
 */
static VALUE
obj_to_enum(argc, argv, obj)
    int argc;
    VALUE *argv;
    VALUE obj;
{
    VALUE meth = sym_each;

    if (argc > 0) {
        --argc;
        meth = *argv++;
    }
    return rb_enumeratorize(obj, meth, argc, argv);
}