Height is 'a function of' age in children. [=the height of children increases as their age increases]
His bad health has prevented him from being able to 'function' effectively in recent weeks.
Her chief/main/primary/principal 'function' is to provide expert legal advice.
(..) To the untrained eye, I look like a total idiot. You do, in fact. Ah. But it's actually a seduction technique known as "peacocking." My outfit serves the dual function of icebreaker and attention-getter. You can go in now. Watch. Are you peacocking? Really? You think that's gonna work? (..)2009 17 Again