1. It is easier to teach functions than grammar.
.....In my opinion I agree with this comments, because functions are simply language that we use to exchange information. Talking about something students are interested which they intended studying English. Grammar is "rules" of a language which too much complicated. it is one (of many) reasons why students come to hate studying English.
2. Functions contain too much complicated grammar for beginner learners.
.....In my opinion I disagree with this comments, because we can adapt and adopt content for level learners.
3. Learners don't need to learn the names of the functions - just some of the exponents.
.....In my opinion I disagree with this comments, because students do need to know and understand the names of the functions for communication correct way in daily life.