Function Differences: f and f(n) vs. (f \circ g)(n)

[Swapnil]

What is exactly the difference between $$f$$ and $$f(n)$$ and why can't we write $$(f \circ g)(n)$$ as $$f(n) \circ g(n)$$?

 

[Eighty]

f is the function, f(n) is the value of the function at the point n. The ball operator $$\circ$$ acts on functions, not values, so your second expression is wrong.

 

[d_leet]

You can, however, write it as f(g(n)).

 

[hashimcom]

u can write it
no proplem...i thenk