In section 2.4 (p. 46) of the book Artificial Intelligence: A modern approach (3rd edition), Russell and Norvig write
The job of AI is to design an agent program that implements the agent function — the mapping from percepts to actions.
After that, in section 2.4.1, they write
Notice the difference between the agent program, which takes the current percept as input, and the agent function, which takes the entire percept history.
Why does the agent program only take current percept? Isn't the agent program just an implementation of the agent function?
So, what is the difference between an agent function and an agent program (with respect to the percept sequence)?