Yeah,so I automatically use either COMPOSE(F,FLOOR) or F(x)+(F(x+1)-F(x))*(x-floor(x)) (i.e STEP or LERP)
there are some real functions like that:sigmoid,tanh,arctan,etc(here i mean real functions,not complex functions,if you extend stuff into complex domain weird stuff start to happen,arcsin/arccos stops to have abillity to restrict domain,sin/cos/arctan lies out of its codomain,etc)