I think when calling a curried function it isn't easy to differentiate between a simple function application and a partial (function) application. I would make the assumption that as long as a higher-order function is called, then what we're actually doing is a function transformation and thus a partial application - when we applied all arguments except the last one, then finally, when the last argument of a first-order function (= the partially applied higher-order function) is applied, then this function can not be transformed anymore and is simply just evaluated. I'm sure there's also a difference in lazy evaluated languages and others in there, but this is beyond my competence.