Exercise 11.4 ThinkJulia

New to Julia
1

here’s the text of the exercise:
Memoize the Ackermann function and see if memoization makes it possible to evaluate the function with bigger arguments.
I understand what memoization is, and i did with the fibonacci serie. I can’t understand how can i do it with the Ackermann function since it has two arguments , and not only one as the fibonacci serie.

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2

Is that book advising to use Memoize.jl or something else?

@memoize can handle multiple arguments

3

no, he’s not advising to use that package.

4

Can you show your fibonacci solution? Then it’s easier for people here on the forum to expand on that for ackerman

5

A two-argument function is (conceptually) the same as a function with a single argument, a tuple of 2 numbers. You can memoize by doing whatever you did for one-parameter functions, but using (x, y) as your key.

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6 
known = Dict(0=>0, 1=>1)

function fibonacci(n)
    if n ∈ keys(known)
        return known[n]
    end
    res = fibonacci(n-1) + fibonacci(n-2)
    known[n] = res
    res
end

that’s the fibonacci using memoization