The set of primitive recursive functions is [...] the smallest set containing the constant 0, the successor function, and projection functions, and closed under composition and primitive recursion.
My question is about the way composition, which does not seem very intuitive to me
If is a -ary function and are -ary functions on the natural numbers, the composition of with is the -ary function defined by
Is this just another way of stating composition as one may understand it in real analysis: that if we have
then we can define some composed function
Or, would there be any "risk" at looking at the definition in this simplistic way?