This over-generalization of vague concepts isn't helpful. An example of DRY would be: You're using libraries "foo" and "baz," and whenever foo::get_bar() retur

This over-generalization of vague concepts isn't helpful. An example of DRY would be: You're using libraries "foo" and "baz," and whenever foo::get_bar() returns 1, 2, or 3, you need to call (for your use-case) baz::qux(9), baz::qux(31), or baz::qux(-5), respectively. So you create one function that either handles both calls completely, or at least maps the return value from get_bar to the argument required by qux. The violation of DRY would have switch statements littered throughout the code that all do the same mapping manually. A build-or-"buy" decision isn't about being DRY or not.